The wall length is 3 times the height.
The area of the wall is 300 sq. ft.
Height H = X
Length L = 3X
Area S = H x L = X x 3X = 300
3(X x X) = 300
X x X = 300/3 = 100
X = 10
a. What are the dimensions of the wall?
Height H = X = 10 ft
Length L = 3X = 30 ft
b. If each can of paint covers 22 sq. ft?, will 12 cans be enough to cover the wall?
12 cans will cover 22 x 12 = 264 sq. ft
The mural is 300 sq. ft.
So, 12 cans is not enough. You will need 14 cans.