Answer
$A=(1/2)(ma+b)(a)(a+\frac{b}{m})$
Work Step by Step
The length of the first base is a. The length of the second base is equal to a plus the x-intercept. Thus, this is given by: $ a + \frac{b}{m}$. Finally, the height is the y-value where the two lines intersect, which is: $ y = ma + b$ Thus, the equation is:
$A = (1/2)(h)(b_1+b_2) = (1/2)(ma+b)(a)(a+\frac{b}{m})$
