Answer:
EASY! First we have to find the area of the back yard.
Explanation:
![A=12*10\\A=120](https://img.qammunity.org/2021/formulas/mathematics/middle-school/rgcm9z44gzttfkf3yxll6chhrxm3pgh9f5.png)
So, we have to convert feet to yards(as it's in feet and we are doing our calculations in yards).
(And also, due to the fact it's squared, we have to square our coefficient as well).
The formula states we have to divide by 3, thus:
![(400)/(3^(2) ) =(400)/(9 )=44.444...](https://img.qammunity.org/2021/formulas/mathematics/middle-school/9d1re8b5imcowuv44cuyg5zu0nzlw8v6lt.png)
Hmmm. Might be better if we do it the other way around. Might be simpler.
Thus:
![120*9=1,080](https://img.qammunity.org/2021/formulas/mathematics/middle-school/nuak3rchb83t1ytjpjfukrh8h87t9gy8o0.png)
So then we divide 1,080 by 400, as the bag covers 400 feet
![(1080)/(400) =2.7](https://img.qammunity.org/2021/formulas/mathematics/middle-school/rjazjy1srgrn3su7g63mye8nxikqq3bjec.png)
So, he needs 3 bags(as he cannot use two to cover the entire back yard). He will have a little left over, but that's okay, because he cannot buy 0.7 of a bag.
Then we multiply this by the cost!
![3*25.99=77.97](https://img.qammunity.org/2021/formulas/mathematics/middle-school/x4o99ywodyvx5e5heonhdau4wi8ziqc3hp.png)
So, Kenneth would have to pay $77.97 and have a little left over!
Hope I did this right!
Hope this helps!
P.S. How are you doing during this shelter-in-place?