The answer is 15
To find the answer set up an equation like this
a2 + b2 = c2 (2 means squared)
Here we are trying to find the value of a so we know the values of b and c.
a2 + 20(squared) = 25(squared)
20 squared equals 400
25 squared equals 625
a2 + 400 = 625
Subtract 400 from 625 which equals 225.
Now we find the square root or closest square root of 225.
The square root of 225 is 15. 15 x 15 = 225
