Question

If a varies directly as b, and a = 28 when b = 7, find b when a = 5.

Answer 1

"a varies directly as b" means a = kb, where k is a constant.

it tells us that a = 28 when b = 7, so plug these into a = kb and solve for k

now, to find b when a = 5, plug in k and a into the equation and solve for b