To answer this you need to use the Pythagorean theorem, the first part it 4^2+x^2=7^2 so the answer to the bottom x is 5.7. Your next step is to do the Pythagorean theorem for the whole triangle so your equation would be 10^2 + 5.7^2= x^2 once you solve that you will get 132.49 which you need to take the square root of. Once you will do that you will find the other x = 11.5
