Question 807057
this can be solved using pathagorias theorm

a^2 + b^2 = c^2

9^2 + b^2 = 15^2
81 + b^2 = 225
subtract 81 from both sides
b^2 = 144

square root of 144 is 12
so your screen is 12 inches wide and 9 inches high with a diagonal of 15 inches