Найдите произведение: а) 2/7 * 5/4; б) 5/8 * 4/5; в) 9/25 * 2 1/7 * 1 5/9.

а) 2/7 * 5/4 = (2 * 5) / (7 * 4) = 10/28 = 5/14; б) 5/8 * 4/5 = (5 * 4) / (8 * 5) = 20/40 = 1/2; в) 9/25 * 15/7 * 14/9 = (9 * 15 * 14) / (25 * 7 * 9) = 210/175 = 6/5.