c=m+fx
m+5f=25 and m+10f=40 solving both for m
m=25-5f and m=40-10f, since f=f, the fee is the same, we can now say:
25-5f=40-10f subtract 25 from both sides
-5f=15-10f add 10f to both sides
5f=15 divide both sides by 5
f=3, now we can solve for the membership fee, m, using either original equation...
m+5f=25, f=3 so
m+5(3)=25
m+15=25
m=10
So the membership fee is $10 and the lesson fee is $3 per session.