Вычислим по действиям -7/8 - (-1 4/7) + (-4/21) * 10 1/2:
1) -4/21 * 10 1/2 = -4/21 * 21/2 = -4/2 = -2;
2) -7/8 + 1 4/7 = -7/8 + 8/8 + 4/7 = 1/8 + 4/7 = (4 * 8 + 1 * 7)/56 = 39/56;
3) 39/56 - 2 = -1 17/56.
Вычислим по действиям -7/8 - (-1 4/7) + (-4/21) * 10 1/2:
1) -4/21 * 10 1/2 = -4/21 * 21/2 = -4/2 = -2;
2) -7/8 + 1 4/7 = -7/8 + 8/8 + 4/7 = 1/8 + 4/7 = (4 * 8 + 1 * 7)/56 = 39/56;
3) 39/56 - 2 = -1 17/56.