The congruent sides of an isosceles triangle are each 5 cm long, and the perimeter is 17 cm. In centimeters, what is the length of the base?
I know that the perimeter of a triangle is the sum of the lengths of its three sides. So, if the two congruent sides are each 5 cm long, then the base must be 17 - 5 - 5 = 7 cm long.

