Answer:
6m + 3n.
Step-by-step explanation:
The area of a trapezoid = h/2 (a + b), where h = altitude and a and b are the lengths of the opposite parallel sides.
So here:
h = 6, a = m and b = m+n.
So area = 6/2(m + m + n)
= 6/2(2m + n)
= 3(2m + n)
= 6m + 3n.
