Вычислить. (1/4-2/3)*(4/5-2/15)*(-3/5) . (1/6-5/9)*(1/2-3/7)7. 1/5

(1/4 - 2/3) * (4/5 - 2/15) * (-3/5) = 1/6.
1). 1/4 - 2/3 = (1 * 3)/(4 * 3) - (2 * 4)/(3 * 4) = 3/12 - 8/12 = -5/12;
2). 4/5 - 2/15 = (4 * 3)/(5 * 3) - 2/15 = 12/15 - 2/15 = 10/15;
3). -5/12 * 10/15 = -(5 * 10)/(12 * 15) = -50/180. = -5/18;
4) -5/18 * (-3/5) = (5 * 3)/(18 * 5) = 15/90 = 1/6.

(1/6 - 5/9) * (1/2 - 3/7) * 1/5 = -1/180.
1). 1/6 - 5/9 = (1 * 9)/(6 * 9) - (5 * 6)/(9 * 6) = 9/54 - 30/54 = -21/54 = -7/18;
2). 1/2 - 3/7 = (1 * 7)/(2 * 7) - (3 * 2)/(7 * 2) = 7/14 - 6/14 = 1/14;
3). -7/18 * 1/14 = -(7 * 1)/(18 * 14) = -7/252 = -1/36;
4). -1/36 * 1/5 = -(1 * 1)/(36 * 5) = -1/180.