66 vă rog dau coroana REPEDEEE

Răspuns:
f=5*(v-1)+2=>f=5*v-5+2=>f=5*v-3
f=7*(v+1-2)+2=>f=7*(v-1)+2=>f=7v-7+2=>
f=7v-5
7v-5=5v-3
7v-5v=8
2v=8
v=4