Geomertry
posted by Mary .
The surface area of a rectangular prism is 190 square inches, the length is 10 inches, and the width 3 inches. Find the height.

Substitute 4d for e in second equation and solve for d. Insert that value into the first equation and solve for e. Check by inserting both values into the second equation.
See your later post. 
The following areas are equal:
1. Front and Back.
2. Left and right.
3. Top and Bottom.
Therefore, we calculate 3 areas and
multiply each by 2 to get the 6 areas:
As=2(3*h) + 2(10*h) + 2(10*3)=1901n^2.
6h + 20h + 60 = 190,
26h = 190  60 = 130,
h = 5in.