area = length x width
x² + 12x = l * x
A.
First, you factor x from x² + 12x
[tex] x^{2} +12x=x(x+12)[/tex]
area = x (x+12)
area = (x+12) * x
Length = x + 12
B.
If x = 10,
l = x + 12 = 10 +12 = 22
length = 22
and
Area = x² + 12x = 10² + 12(10) = 100 + 120 = 220
area = 220
Hope this helps :)