Answer:
26) Let the first number be x.
Sum of three consecutive even numbers:
![x+(x+2)+(x+4)=-84](https://img.qammunity.org/2021/formulas/mathematics/college/aavvr9r2lwqdxfo8pbrtgcd1ycx1xgf419.png)
![x+x+2+x+4=-84\\](https://img.qammunity.org/2021/formulas/mathematics/college/8phzpilvn21507ctilog9tw9om9qzyleqi.png)
![3x+6=-84](https://img.qammunity.org/2021/formulas/mathematics/college/qu3irbjrveiipzm4t6x7wdj1raub9kngug.png)
Subtract 6 from both sides:
![3x+6-6=-84-6](https://img.qammunity.org/2021/formulas/mathematics/college/12c8k4soyru9xo256mv94oddt1jg2ka1el.png)
![3x=-90](https://img.qammunity.org/2021/formulas/mathematics/college/fw5zrm8ka45hmp80mo5ilhqzesoqojcc2b.png)
Divide both sides by 3:
![(3x)/(3)=(-90)/(3)](https://img.qammunity.org/2021/formulas/mathematics/college/woc1rmzymj3zspu2nlmcd8065ltpoy2ptp.png)
![x=-30](https://img.qammunity.org/2021/formulas/mathematics/college/ry9p76mpvr89442g8tlss7qnjvnq9w41xn.png)
To find the other two numbers, add 2 and 4 respectively:
![(-30+2=-28)(-30+4=-26)](https://img.qammunity.org/2021/formulas/mathematics/college/8ol25ntj9mv4vwu10t5ej0y64j938sbkbh.png)
27) Let the first number be x.
Sum of three consecutive odd integers:
![x+(x+2)+(x+4)=141](https://img.qammunity.org/2021/formulas/mathematics/college/avrvrf7cjrz3l90kuagk7casnwvm5c77rv.png)
![3x+6=141](https://img.qammunity.org/2021/formulas/mathematics/college/4ooevad8hg6yfctc3klv4ixj4d4vgsu8d9.png)
Subtract 6 from both sides:
![3x+6-6=141-6\\3x=135](https://img.qammunity.org/2021/formulas/mathematics/college/qzn4g2ssywpjcws3nztbei6aq6rkt1mi8i.png)
Divide both sides by 3:
![(3x)/(3)=(135)/(3)\\x=45](https://img.qammunity.org/2021/formulas/mathematics/college/ctvciayz1l7drqxldbawlv2gtpadlbiyc8.png)
To find the other two numbers, add 2 and 4 respectively:
![(45+2=47)(45+4=49)](https://img.qammunity.org/2021/formulas/mathematics/college/jllctb03c3w1893bq77zsaakacub93ikas.png)
28) Let the first number be x.
Sum of four consecutive integers:
![x+(x+1)+(x+2)+(x+3)=54](https://img.qammunity.org/2021/formulas/mathematics/college/8qt8fkc8w9b0tnp0zvb0vjavqy370qtaum.png)
![4x+6=54](https://img.qammunity.org/2021/formulas/mathematics/college/v7fs218ico377kc1mac52xajugh6o16emx.png)
Subtract 6 from both sides:
![4x+6-6=54-6\\4x=48](https://img.qammunity.org/2021/formulas/mathematics/college/ajop2tf7oewxvadfdwsef7konuf96v8e1n.png)
Divide both sides by 4:
![(4x)/(4)=(48)/(4)\\x=12](https://img.qammunity.org/2021/formulas/mathematics/college/xcdyv75ejnfusysh56ptddngfr24hqk3v2.png)
To find the other three numbers, add 1, 2 and 3 respectively:
![(12+1=13)(12+2=14)(12+3=15)](https://img.qammunity.org/2021/formulas/mathematics/college/yh5sdspg49ucam1yi0jr14xudiz0zrvscv.png)
29) Let the first number be x.
Sum of four consecutive integers:
![x+(x+1)+(x+2)+(x+3)=-142](https://img.qammunity.org/2021/formulas/mathematics/college/stusvkba30o4uk24frnl44wvshcvrlrelu.png)
![4x+6=-142\\](https://img.qammunity.org/2021/formulas/mathematics/college/j9dop6omssdp6rmz491oo9p6okre07e11g.png)
Subtract 6 from both sides:
![4x+6-6=-142-6](https://img.qammunity.org/2021/formulas/mathematics/college/ft9bjifor3jitrbxk8135942h4o49b8f9m.png)
![4x=-148](https://img.qammunity.org/2021/formulas/mathematics/college/2l48erl8ngu6v7nph25tmowhky8cons3m7.png)
Divide both sides by 4:
![(4x)/(4)=(-148)/(4)\\x=-37](https://img.qammunity.org/2021/formulas/mathematics/college/h7k7qpoinut4xmw9dafteeaangha1noig7.png)
To find the other three numbers, add 1, 2 and 3 respectively:
![(-37+1=-36)(-37+2=-35)(-37+3=-34)](https://img.qammunity.org/2021/formulas/mathematics/college/s4l4necan03zd398l1sjxjzo6zp08fg4yt.png)