Which variable is most important to the following problem?

Janet played the first 13 minutes of the game. Thomas then replaced her for the rest of the half. Thomas started the second half and was replaced by Janet with 21 minutes left in the game. If each half is 35 minutes long, how many minutes did Thomas play?
O the legth of a half
• the number of players on a team
• the amount of time Thomas played

The variable that is most important to this problem is the length of a half.