3/8*х+25=100

1/9*х-20=56

7/15*х-50 3/4=19 1/4 (19 целых одна четвёртая)

40-3/8*х=35 1/2

(2 4/5*х-50) : 2/3=51

(4 1/2-2*х) * 3 2/3=11/15

остальные тоже дроби.

1)

3/8 * х + 25=100

3/8*х = 100-25

3/8 * х = 75

х = 75 : 3/8 = 75/1 * 8/3 = (25*8) / 1

х = 200

2)

1/9 * х - 20=56

1/9*х = 56+20

х = 76 : 1/9 = 76/1 * 9/1

х = 684

3)

7/15 * х - 50 3/4 = 19 1/4

7/15 * х = 19 1/4 + 50 3/4

7/15 * х = 70

х = 70 : 7/15 = 70/1 * 15/7 = 10*15

х=150

4)

40 - 3/8 * х = 35 1/2

-3/8 * х = 35 1/2 - 40

-3/8 * х = - 4 1/2

х = - 4 1/2 : (- 3/8) = 9/2 * 8/3 = (3*4) / (1*1)

х=12

5)

(2 4/5 * х - 50) : 2/3 = 51

2 4/5 * х - 50 = 51/1 * 2/3

2 4/5 * х - 50 = 102/3

2 4/5 * х = 34 + 50

х = 84 : 2 4/5 = 84: 14/5 = (84*5) / (1*14) = 6*5

х=30

6)

(4 1/2 - 2*х) * 3 2/3 = 11/15

4 1/2 - 2*х = 11/15 : 3 2/3

4 1/2 - 2*х = 11/15 * 3/11

4 1/2 - 2*х = 1/5

2 х = 4 1/2 - 1/5

2 х = 4 5/10 - 2/10

2 х = 4 3/10

х = 4 3/10 : 2 = 43/10 * 1/2 = 43/20

х = 2 3/20

х = 2,15

1

3/8*x=100-25

3/8*x=75

x=75:3/8=75*8/3

x=200

2

1/9*х-20=56

1/9*x=56+20

1/9*x=76

x=76:1/9=76*9

x=684

3

7/15*х-50 3/4=19 1/4

7/15*x=50 3/4+19 1/4

7/15*x=70

x=70:7/15=70*15/7

x=150

4

40-3/8*х=35 1/2

3/8*x=40-35 1/2

3/8*x=4 1/2

x=4 1/2:3/8=9/2*8/3

x=12

5

(2 4/5*х-50) : 2/3=51

2 4/5*x-50=51*2/3

2 4/5*x-50=34

2 4/5*x=34+50

2 4/5*x=84

x=84:2 4/5=84*5/14

x=30

6

(4 1/2-2*х) * 3 2/3=11/15

4 1/2-2x=11/15:3 2/3=11/15*3/8

4 1/2-2x=11/40

2x=4 1/2-11/40=4 20/40-11/40

2x=4 9/40

x=4 9/40:2=169/80

x=2 9/80