Okay so, you use A^2+B^2=C^2 A is 28 (side.) And C (hypotenuse) is 53. So, 28^2+B^2=58^2 (^2 is squared) We dont know what the other side is, so we keep it “B.” 28 squared is 784. 53 squared is 2,809. So now, we take away ^2 since it was already squared. 784+B^2=2,809 Now, we subtract 784 from both sides 784+B^2=2,809 -784 -784 B^2= 2,025 Then you do the opposite of squaring, you square root 45. the missing side is 45