Выполни действие при меняя распределительный закон умножения. 7/12*4/21+5/12*4/21=. 2цел2/17*1цел5/6минус1цел5/6*1цел2/17. (. (3цел4/15+4цел5/6)*(3цел17/18минус2цел5/9)=

а) 7/12 * 4/21 + 5/12 * 4/21 = 4/21 * (7/12 + 5/12) = 4/21 * 1 = 4/21.
б) 2 2/17 * 1 5/6 - 1 5/6 * 1 2/17 = 36/17 * (11/6 - 11/6) = 36/17 * 0 = 0.
    2 2/17 = (2 * 17 + 2)/17 = 36/17.
    1 5/6 = (1 * 6 + 5)/6 = 11/6.
в) (3 4/15 + 4 5/6) * (3 17/18 - 2 5/9) = 11 1/4.
    3 4/15 = (3 * 15 + 4)/15 = 49/15.
    4 5/6 = (4 * 6 + 5)/6 = 29/6.
    3 17/18 = (3 * 18 + 17)/18 = 71/18.
    2 5/9 = (2 * 9 + 5)/9 = 23/9.
 1. 49/15 + 29/6 = (98 + 145)/30 = 243/30 сократим на 3 = 81/10.
 2. 71/18 - 23/9 = (71 - 46)/18 = 25/18.
 3. 81/10 * 25/18 = (81 * 25)/(10 *18) = 2025/180 сократим на 45 = 45/4 = 11 1/4.