1. 3/5÷8/15+3(1/4)*3/13=9/8+9/52=117/104+18/104=135/104
2. а) 1/8х=12
х=96
б) 4у-12.8
4у=12.8
у=3.2
в) 5х+1.8=3х-2
5х-3х=-2-1.8
2х=-3.8
х=-1.9
г) 6х-3(3х-2)=18
6х-9х+6=18
-3+6=18
-3х=18-6
-3х=12
х=-4
3. (2.151÷0.09-5.9)*0.52÷1.6=65.8*0.52÷1.6=34.216÷1.6=21.385
4. 2(2/3)÷3(6/7)=1(7/9)÷х
2(2/3)÷3(6/7)=1(7/9)÷х, х≠0
2*2*1/3*2/7=7/9*1/х
8/21=7/9х
72х= 147
х=49/24, х≠0
х=49/24
х=2(1/24)
5. 0.7а-9, при а=-5
0.7-5-9=0.7-14=-13.3