Question

The formula for a trapezoid relates the area A, the two bases, a and b, and the height, h.

Answer 1

First you switch sides (a+b)/2 h=A
Then  Multiply the fractions h(a+b)/2 =4
Multiply both sides by 2  2h (a+b/2 =2a
Simplfy h(a+b) = 2a 
Divide both sides by h 
simplfy
Subtract b form both sides 
your answer a=bh−h+2

Answer 2

multiply both sides by 2 to get

2A = (a+b)*h

divide both sides by h

 to get 2A/h = a+b

 subtract b from both sides to get a = 2A/h -b

3rd choice is correct