Question

Please help me

Answer 1

Use Pythagorean theorem
a^2 + b^2 = c^2
Other words, lengths of the shortest sides squared are equal to the longest squared

a^2 + 9^2 = 15^2
a^2 + 81 = 225
a^2 = 144
a = squareroot of 144
a = 12

Solution: a = 12