1) х-2 1/5=5 1/20

2) 10 2/7-х=2 1/2

3) х+4 2/3=6 1/4

1) х-2 1/5=5 1/20

х - (2*5+1) / 5 = (5*20+1) / 20

х-11/5=101/20

х=101/20+11/5

х=101/20 + (11*4) / (5*4)

х=101/20+44/20

х=145/20 сократим на 5

х=29/4=7 1/4

2) 10 2/7-х=2 1/2

х=10 2/7-2 1/2

х = (10*7+2) / 7 - (2*2+1) / 2

х=72/7-5/2

х = (72*2) / (7*2) - (5*7) / (2*7)

х = (144/14) - (35/14)

х = (144-35) / 14

х=109/14=7 11/14

3) х+4 2/3=6 1/4

х=6 1/4-4 2/3

х = (6*4+1) / 4 - (4*3+2) / 3

х = (25/4) - (14/3)

х = (25*3) / (4*3) - (14*4) / (3*4)

х = (75/12) - (56/12)

х = (75-56) / 12

х=19/12=1 7/12