Take into accoun that the Pythagorean theorme is given by:
c² = a² + b²
8.
a = ?, b = 18, c = 30
solve the equation for a:
c² = a² + b²
a² = c² - b²
a = √(c² - b²) replace the values of c and b
a = √(30² - 18²)
a = √(900 - 324)
a = √(576)
a = 24
9.
c= ?, a = 5, b = 12
replace the values of b and a:
c = √(a² + b²)
c = √(5² + 12²)
c = √(25 + 144)
c = √(169)
c = 13
10.
b = ?, a = 6, c = 10
solve the equation for b:
b = √(c² - a²)
b = √(10² - 6²)
b = √(100 - 36)
b = √(64)
b = 8