Let C be the cost per round and F be the fee to use the golf course.
When John plays 3 rounds of golf, he pays a total of F+3C.
When John plays 4 rounds of golf, he pays a total of F+4C.
Use these expressions to write down a system of equations, taking into account that John paid $50 to play 3 rounds and $60 to play 4 rounds:
Solve this system using the elimination method. Substract the first equation from the second equation:
Replace C=10 into the first equation to find the value of F:
Therefore, the cost per round is $10 and the fee to use the golf course is $20.