Answer:
a.) 10 months
b.) Kool Karate
c.) Karate Klub
Explanation:
Karate Klub : y=25x+200
Kool Karate : y=35x+100
A.) First, set the equations equal to each other then solve for x.

take away 100 from both sides

take away 25x from both sides

divide 10 from both sides so x can be by itself and equal to 1

This means that at 10 months, the cost is the same for both.
B.) Substitute 6 for x in both equations
Karate Klub :

Kool Karate :

The cost for Kool Karate is cheaper, so that is what he should join.
C.) Substitute 12 for x in both equations.
x=12 because there are 12 months in a year.
Karate Klub:

Kool Karate:

The cost for Karate Klub is cheaper, so that is what he should join.