1) (3/4+1/5) * 5/19

2) (12 1/3 - 7 3/4) * 6/11

3) (2 3/5 - 5/8) : 19 3/4

1) (3/4+1/5) х5/19=1 1/4

3/4+1/5=15/20+4/20=19/20

19/20 х5/9=19/4 х5/19=5/4=1 1/4

2) (12 1/3-7 3/4) х6/11=2 1/2

12 1/3-7 3/4=5 1/3-3/4=16/3-3/4=64/12-9/12=55/12

55/12 х6/11=5/2=2 1/2

3) (2 3/5-5/8) : 19 3/4=1/10

2 3/5-5/8=13/5-5/8=104/40-25/40=79/40

79/40:19 3/4=79/40:79/4=79/40 х4/79=1/10

1) (3/4 + 1/5) * 5/19 = (15/20 + 4/20) * 5/19 = 19/20 * 5/19 = 5/20 = 1/4 = 0,25; 2) (12 1/3 - 7 3/4) * 6/11 = (12 4/12 - 7 9/12) * 6/11 = (11 16/12 - 7 9/12) * 6/11 = 4 7/12 * 6/11 = 55/12 * 6/11 = 5/2 = 2,5; 3) (2 3/5 - 5/8) : 19 3/4 = (2 24/40 - 25/40) : 19 3/4 = (1 64/40 - 25/40) : 19 3/4 = 1 39/40 : 19 3/4 = 79/40 : 79/4 = 79/40 * 4/79 = 1/10 = 0,1.