What is the length of ac ? enter your answer in the box. =units

That's an isosceles triangle lying on its side.  The base angles (on the left) are marked equal, so we know the sides opposite them are equal.

That means that  . . . x+4 = 3x-8

Subtract 'x' from each side . . . 4 = 2x-8

Add  8  to each side . . . 12 = 2x

Divide each side by 2 . . . 6 = x

problem:

f(x) = - 2/3x + 5; f(5/2)

substitute 5/2 in for x:

f(5/2) = -2/3(5/2) + 5

simplify the right side:

f(5/2) = -5/3 + 5

f(5/2) = 10/3

f(5/2) = 10/3

i hope this !

i think that you should ask google for the answer to that problem because if we don't know it google does