0.75 + (- 2 5 / 7) - (- 0.125) + (- 12 5 / 7) - 4 1 / 8

0.75 + (- 2 5 / 7) - (- 0.125) + (- 12 5 / 7) - 4 1 / 8

∵ original formula = 0.75-19 / 7 + 0.125-89 / 7-33 / 8 = 0.75 + 0.125-19 / 7-89 / 7-33 / 8 = 0.875-108 / 7-33 / 8
=-18.68
0.75 + (- 2 5 / 7) - (- 0.125) + (- 12 5 / 7) - 4 1 / 8 = 18.68

Solution ratio X: 7.5 = 2.1:1.8 6.5x: 3 = 10:9

x：7.5=2.1：1.8
1.8x=7.5*2.1
x=7.5*2.1/1.8
x=8.75
6.5x：3=10：9
9*6.5x=10*3
x=30/(9*6.5)
x=20/39

2 (5x-1) + 5 (x-1) = 0.8 solution proportion: 6 (x-1) = 7 (x-3)
I'm in a hurry,

Solution equation: 0.2 (5x-1) + 5 (x-1) = 0.8
x-0.2+5x-5=0.8
6x=5.2+0.8
x=1
Solution proportion: 6 (x-1) = 7 (x-3)
6x-6=7x-21
7x-6x=21-6
x=15