Ответ:

1. 7/2=3у-0,5/5

3у-0,5=7*5/2

3у-0,5=35/2

3у=35/2+1/2

3у=36/2=18

у=6

2. 5 1/7 / (1/14) = 1 3/4 / (7/18) * x

36/7 *14= 7/4 * 18/7х

36 * 2 = 1/2 * 9x

72 = 9/2 * x

9/2 * x = 72

x = 16

3. (8, 1)/(0, 9) = 3/(x - 4)

х≠4

(81/10)/(9/100) = 3/(x - 4)

90 = 3/(x - 4)

90(x - 4)=3

30(x - 4) = 1

30x - 120 = 1

30x = 1 + 120

30x = 121

x = 121/30;x≠4