Answer:
15 inches
Step-by-step explanation:
The longest side of the right triangular window frame is 39 inches
The height is 36 inches
Let the base of the window frame be x inches
So according to Pythagoras theorem,
x² + 36² = 39²
x² = 39² - 36² = 225
x = = 15 inches
The third side of the window frame is therefore equal to 15 inches.
