А) 4 11/18 * 6/7 = 83/18 * 6/7 = (83*1)/(3*7) = 83/21 = 3 20/21
б) (1 1/2)^3 - 2 1/4 * 1 1/3 = 3/8
1) 1 1/2 * 1 1/2 * 1 1/2 = 3/2 * 3/2 * 3/2 = 27/8 = 3 3/8
2) 2 1/4 * 1 1/3 = 9/4 * 4/3 = 9/3 = 3
3) 3 3/8 - 3 = 3/8
2а + 4 - 10 = 18 - 6а
2а + 6а = 18 + 10 - 4
8а = 24
а = 3
-------------------------------
6у - 3 + 18у - 24 = 83 + 5у - 15
6у + 18у - 5у = 83 + 3 + 24 - 15
19у = 95
у = 5
640:(х*9+8)=8
9х+8=640:8
9х+8=80
9х=80-8
9х=72
х=72:9
х=8