How to use subsitution method

Carson has only $20 bills and $10 bill in her wallet. the total value of the bills is $50. she has 1 more $20 bill than $10 bills. how many each kind of bill does carson have? a. one $20 and two $10 bills b. two $20 bills and one $10 bill c. one $20 bills and three $10 bills d. two $20 bills and two $10 bills

Which of the following answers is 5/25 simplified? 1/5 5/5 2/5 1/25

Ihonestly have no clue if it's each or none.