Hello it should be 220ft not 220f!
Slope or gradient is vertical rise divided by horizontal rise
80ft/220ft = 4/11
Tan(angle) = opposite/ adjacent
tan(42) = 67/x
x =67/tan(42)
X = 74.411
rounded to nearest tenth : x = 74.4
x²-8x=768
x²-8x-768=0
(x-32)(x+24)=0
x=32 x=-24
you use 32 because it can be negative
plug in for x
(32)(32-8)(1)=768
32×24=768
this isn't the completing the square method though this is zero product law