Find the unknown side lengths in similar triangles PQR and ABC.
Triangle P Q R has sides of the following lengths: P Q, a; Q R, 40; P R, b.
Triangle A B C has sides of the following lengths: A B, 21; B C, 35; A C, 28.B P R Q C A 21 28 35 40 a b
(Simplify your answers. Type an integer or a fraction.)