Hello!
The answer is:
It will take 42.35 minutes to weed the garden together.
Why?
To solve the problem, we need to use the given information about the rate for both Laura and her husband. We know that she can weed the garden in 1 hour and 20 minutes (80 minutes) and her husband can weed it in 1 hour and 30 minutes (90 minutes), so we need to combine both's work and calculate how much time it will take to weed the garden together.
So, calculating we have:
Laura's rate:
![(1garden)/(80minutes)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/pp9en43qaxlgbgkqg2nojfosmkxtxg4nhk.png)
Husband's rate:
![(1garden)/(90minutes)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/8uoo2128k15mro75el2y47azf1v0p6h2is.png)
Now, writing the equation we have:
![Laura'sRate+Husband'sRate=CombinedRate](https://img.qammunity.org/2020/formulas/mathematics/middle-school/kybzqttpl6hgwvnwaqhhfi40ffroxldhgt.png)
![(1)/(80)+(1)/(90)=(1)/(time)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/chhkcoeo1syabku2041866iq7arau4uiz1.png)
![(1*90+1*80)/(7200)=(1)/(time)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/j07i6ofidwverh7457xozrq5llfmtfcogs.png)
![(170)/(7200)=(1)/(time)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/f4ecnkwre6iva56hu8luzgsm91sbx9vz0t.png)
![(17)/(720)=(11)/(time)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/png4xdje4bzlmbck54drdwx3p7k4qqzcjc.png)
![(17)/(720)=(1)/(time)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ebnuipv7yfar1u9e5k3isgx0cc5ywuaxvn.png)
![(17)/(720)*time=1](https://img.qammunity.org/2020/formulas/mathematics/middle-school/us6eo4b95zgomdalc3otb2qldihrcp5m69.png)
![time=1*(720)/(17)=42.35](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ssuzdba6fyugspcmzl5cj9xc812n8xpvg4.png)
Hence, we have that it will take 42.35 minutes to weed the garden working together.
Have a nice day!