The given triangle is a right triangle because one of its angles is 90 degrees. We would find b by applying the pythagorean theorem which is expressed as
hypotenuse^2 = one leg^2 + other leg^2
From the information given,
hypotenuse = 17
one leg = 7
other leg = b
Thus,
17^2 = 7^2 + b^2
289 = 49 + b^2
b^2 = 289 - 49 = 240
b = √240
b = 4√15
