8
(3a-6b+4)/(6a-3b+4)=7
3a-6b+4=42a-21b+28
42a-21b-3a+6b=-28+4
39a-15b=-24
39a-15b+25=-24+25=1
9
7a/6c-(49a²+36c²)/42ac+(6c-49a)/7a=
=(49a²-49a²-36c²+36c²-294ac)/42ac=
=-294ac/42ac=-7
10
(5a+7b)/(3a+2b)=1
5a+7b=3a+2b
5a-3a=2b-7b
2a=-5b
a=-2,5b
a/b=-2,5b/b=-2,5
11
a/b=7
a=7b
(a+5b+24)/(9a-3b+120)=(7b+5b+24)/(63b-3b+120)=
=(12b+24)/(60b+120)=12(b+2)/60(b+2)=12/60=0,2