Lets name the shortest piece a, the medium b and the longest c
Together they are 90inches
![a + b + c = 90](https://img.qammunity.org/2019/formulas/mathematics/middle-school/jr4gcy2r8m1bpr32ygg4fgbg56hwk087yh.png)
The longest is 30 inches longer than the shortest
![c = a + 30](https://img.qammunity.org/2019/formulas/mathematics/middle-school/z1scp5hbhun7fysuz7q16i0wlegjorr78u.png)
The third piece is half the lenght of the longest
![b = (c)/(2)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/yethhqfxl1xakgxy45nepk76zsxvc7dnf8.png)
So if you place c=a+30 in the other 2 equasions you get
![a + b + (a + 30) = 90 = 2a + b + 30](https://img.qammunity.org/2019/formulas/mathematics/middle-school/cgy2kq3kvzv6hrj7ra3mapygzpsfp461q9.png)
And
![b = (30 + a)/(2)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/ugssmwe4ubhziwry8hz26pmoya4ojenpc7.png)
Now if you put this 2 toghether u get
![2a + (30 + a)/(2) + 30 = 90](https://img.qammunity.org/2019/formulas/mathematics/middle-school/x1rugufu0ty89u4mii0hhb0mwsj84bue3q.png)
Multyplied by 2
![4a + 30 + a + 60 = 180](https://img.qammunity.org/2019/formulas/mathematics/middle-school/wyuj87qb9b61yi6vyj10zx4qfig9ue8lil.png)
![5a = 90](https://img.qammunity.org/2019/formulas/mathematics/middle-school/8pi8hi5pr78p9bwbhb14bp3od07eiruv1y.png)
Meaning that a=18inches
Now that we have the lenght of a we put it in the previous equasion
![b = (30 + 18)/(2)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/cdkay4ooim8dl42hzkmrocwrto8p9nh3eo.png)
So b=48/2 which means b=24inches
And together they must be 90 so
![18 + 24 + c = 90](https://img.qammunity.org/2019/formulas/mathematics/middle-school/oefjtiovlxnvls7cruzfcuxjk0xmrx6l4h.png)
C=48inches