Answer:
20 cm
Step-by-step explanation:
This is a right triangle so we can use the Pythagorean theorem
a^2 +b^2 = c^2
where a and b are the legs and c is the hypotenuse
15^2 +b^2 = 25^2
225+b^2 = 625
Subtract 225 from each side
225+b^2 -225 = 625-225
b^2 = 400
Take the square root of each side
sqrt(b^2) = sqrt(400)
b = 20
