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) * 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.

1)  (3/4+1/5)х5/19=1 1/4
     3/4+1/5=15/20+4/20=19/20
     19/20х5/9=19/4х5/19=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
     55/12х6/11=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=79/40х4/79=1/10