The formula for the area of a trapezoid is : area = (a + b)/2 x height, where a and b are the top and bottom bases.
Using the provided information you have:
25 = (a + b)/2 x 5
Solving for a+ b the first step is divide both sides by 5:
5 = (a + b)/2
Second step is to multiply both sides by 2:
10 = (a +b)
The sun of the bases would be 10 units.