а) 3,8+х=1 4/5

б) 5 2/7+х=-3 9/14

а) 3.8+х=1 4/5

х=1 4/5-3.8

х=1 4/5-3 8/10

х=9/4-38/10

х=18/10-38/10

х=-20/10

х=-2

б) 5 2/7+х=-3 9/14

х=-3 9/14-5 2/7

х=-51/14-37/7

х=-51/14-74/14

х=-125/14

х=-8 13/14

3,8+х = 1 4/5

3,8 = 3 8/10 = 3 4/5

3 4/5+х = 1 4/5

х = 1 4/5 - 3 4/5

х = - 2

проверка: 3,8 + (-2) = 1 4/5; 1,8 = 1,8

5 2/7 + = - 3 9/14

37/7+х = - 51/14

х = - 51/14-37/7

х = (-51-74) / 14

х = - 125/14 = - 8 13/14

проверка

5 2/7 + (-8 13/14) = - 3 9/14

74/14-125/14 = - 51/14

-51/14 = - 51/14