Solve the perimeter formula for an isosceles triangle, P = 2a + b for b.
To solve for b in the formula P = 2a + b for an isosceles triangle, we can rearrange the formula as follows:
P = 2a + b
b = P - 2a
Therefore, the formula for b in terms of the perimeter P and side length a of an isosceles triangle is:
b = P - 2a