This is testing your knowledge on Pythagorean triple.
[tex]60 = 5 \times 12[/tex]
[tex]36 = 3 \times 12[/tex]
Using the Triple 3, 4, 5
[tex]x = 4 \times 12 [/tex]
[tex]x = 48[/tex]
You can also use the Pythagoras theorem.
[tex] {x}^{2} + {36}^{2} = {60}^{2} [/tex]
[tex] {x}^{2} + 1296 = 3600 [/tex]
[tex] {x}^{2} = 2304[/tex]
[tex]x = \sqrt{2304} = 48[/tex]
