Вычислите: 1){3/4+1/5}*5/15= 2){12 1/3-7 3/4}*6/11= 3){2 3/5-5/8}/19 3/4=

1)
3/4+1/5=15/20+4/20=19/20
19/20×5/15=19/60
2)
12 1/3-7 3/4=12 4/12-7 9/12=
=11 16/12-7 9/12=4 7/12
4 7/12×6/11=55/12×6/11=5/2=
=2 1/2
3)
2 3/5-5/8=2 24/40-25/40=
=1 64/40-25/40=1 39/40
1 39/40÷19 3/4=79/40÷79/4=
=79/40×4/79=1/10