1. а) 2xy*7y²=14y²xz
б) -3a*2b*-c=6abc
2. m-3n+5m-7n-7m=m+5m-7m-3n-7n=-m-10n
3.p=a+b+c
a=a
b=a+5
c=1.5a
p=a+a+5+1.5a=3.5a+5
4. 3a+5-12a+6+4a=-5a+11
a=-12
-5*-12+11=60+11=71
5. 5(3a+b)-3(a-4b)=15a+5b-3a+12b=12a+17b
6. y-x-z
(ab-1)-(ab+1)-(ab+2)= ab-1-ab-1-ab-2=-ab-4
7. x-y-(x+xy-xy+y)=x-y-(x+y)=x-y-x-y=-2y