1) - 7/8 + 1 9/20 + 3/10 = -7/8 + 29/20 + 3/10 = -35/40 -58/40 + 3/10 = -93/40 + 3/10 = -93/40 + 12/40 = -81/40 = -2 1/40
2) 4/51 : 1 2/17 * 57/64 = 4/51 : 19/17 * 57/64 = 4*17*57 / 51*19*64 = 3676/62016 = 1/16
3) - 7(6х +3) - 5(4 - х) = -42х - 21 -20 + 5х = -42х - 1 +5х = -37х -1