(30142+z):876=49
30142+z=876*49
30142+z=42924
z=42924-30142
z=12782
13x+15x-24=60
28x=60+24
28x=84
x=84:28
x=3
1) 3/4:5/6=3/4*6/5=18/20=9/10
2)2.1/2*2/5=5/2*2/5=10/10=1
3)1:1.1/6=1*6/7=6/7
4)9/10+1=19/10
5)19/10-6/7=133/70-60/70=73/70=1.3/70