Răspuns:
ab+ac=a(b+c)=7·15=105
ab-ac=a(b-c)=7·7=49
_________
2a+2b=50
2(a+b)=50=>a+b=50:2=>a+b=25
10a+10b=10(a+b)=10·25=250
________
3a+3b+3c=9=>3(a+b+c)=9=>a+b+c=9:3=>a+b+c=3
15a+15b+15c=15(a+b+c)=15·3=45
________
6b+6c=12
6(b+c)=12=>b+c=12:6=>b+c=2
8b-8c=16=>8(b-c)=16=>b-c16:8=>b-c=2
ab+ac=a(b+c)=5·2=10
ab-ac=a(b-c)=5·2=10