The complete question in the figure attached
1) calculate the area <span>all four sides
A=[12+9+12+9]*8=336 ft</span>²
if 1 gallons---------------------------- > covers 350 ft²
X------------------------------------ > 336 ft²
X=336/350=0.96 gallons
but remember
<span>that there are two coats of paint
</span>therefore
0.96*2----------- > 1.92------- > 2 gallons
the answer is 2 gallons
A=b/c -b/d
a+b/d=b/c
(da+b)/d=b/c
db=(da+b)c
c=db/da+b
You use distributive property. So (5 x 2)-(5 x x)= 10 - 5x.