Hey!
You have to use the Pythagorean Theorem.
a² + b² = c² is the same as: c² - b² = a²
[tex] c = 61 \\ 61^{2} = 61 \times 61 = 3,721 [/tex]
[tex] b = 60 \\ 60^{2} = 60 \times 60 = 3,600 [/tex]
Subtract:
[tex] 3,721 - 3,600 = 121 [/tex]
√121 = 11
[tex] \framebox{x = 11 cm} [/tex]
