Answer:
x=10 cm
Step-by-step explanation:
Since this is a right triangle, we can use the Pythagorean theorem
a^2 + b^2 = c^2
x^2 + ( sqrt(200) )^2 = (sqrt(300))^2
x^2 +200 = 300
Subtract 200 from each side
x^2 +200-200 = 300-200
x^2 = 100
Take the square root of each side
sqrt(x^2) = sqrt(100)
x = 10