а) 5х+75=10

5х=10-75

5х=-65

х=-65/5

х=-13

б) 4(х+1)-7х=5

4х+4-7х=5

-3х=1

х=-1/3

в)

[tex]\frac{x+3}{8} = \frac{2x-1}{7}\\ 7(x+3) = 8( 2x-1)\\7x+21 = 16x-8\\7x-16x=-8-21\\-9x = -29\\x=29/9[/tex]

Пошаговое объяснение:

5х + 75 = 10

5х = 10 - 75

5х = -65

х = -65 : 5

х = -13

4(х + 1) - 7х = 5

4х + 4 - 7х = 5

-3х + 4 = 5

-3х = 5 - 4

-3х = 1

х = 1 : (-3)

х = -1/3

(х + 3)/8 = (2х - 1)/7

7(х + 3) = 8(2х - 1)

7х + 21 = 16х - 8

7х - 16х = -8 - 21

-9х = -29

х = -29 : (-9)

х = 29/9

х = 3 2/9