Answer:
24
Step-by-step explanation:
I will assume this is a right triangle with the information given
a^2+b^2 = c^2 is the Pythagorean theorem
18^2 + b^2 = 30^2
Subtract 18^2 from each side
18^2 - 18^2+ b^2 = 30^2 -18^2
b^2 =900 -324
b^2 =576
Take the square root of each side
sqrt(b^2) = sqrt(576)
b =24
