Пошаговое объяснение:

№1

1) 6 7/8 - 3 1/3 = 6 42/48 - 3 16/48 = 3 26/48

2) 3 26/48 + 5 5/16 = 3 26/48 + 5 15/48 = 8 41/48

№2

8/9х * 1 4/5у = 8/9х * 9/5у = (8/9 * 9/5) * х * у =

8/5 * х * у = 8/5ху = 1 3/5ху

№3

8х - 4(16 - 2х) = 8х - 64 + 8х = 16х - 64

№4

(7х + 1) - (9х + 3) = 5

7х + 1 - 9х - 3 = 5

-2х - 2 = 5

-2х = 5 + 2

-2х = 7

х = 7 : (-2)

х = -3,5