Answer: in the 4th month, both amounts would be the same.
Explanation:
Let x represent the number of months it will take each of them to pay the same total amount to be a member of the gym.
The Beginner's Plan is $10 a month plus an initial fee of $60. If Nina buys the Beginner's plan, the total amount that she would pay for x months is
10x + 60
The Veteran's Plan is $15 a month plus an initial fee of $40. If Joe buys the Veteran's plan, the total amount that he would pay for x months is
15x + 40
For both amounts to be the same, the number of months would be
15x + 40 = 10x + 60
15x - 10x = 60 - 40
5x = 20
x = 20/5
x = 4