Hey There!
The formula to calculate for surface area is
2(wh + lw + lh)
Let's plug these numbers in.
2(7*20 + 15*7 + 15*20)
Calculate
7 * 20 = 140
15 * 7 = 105
15 * 20 = 300
Add these numbers up
300 + 105 + 140
= 545
Multiply 545 * 2 = 1090
Therefore, the surface area of the figure would be 1090in
Hope this helped!