Question 819252
f-6=7(s-6)
f=7(s-6)+6
f=7s-42+6
f=7s-36
f+4=3(s+4)
f=3(s+4)-4
f=3s+12-4
f=3s+8
7s-36=3s+8
4s=44
s=11
f=41
check
45=3*15
35=7*5
ok