Shelly and Terrence completed a different number of tasks in a game. Shelly earned 90 points on each task. Terrence's total points were 20 less than Shelly's total. The expression below shows Terrence's total points in the game: 90x − 20

What does the factor x of the first term of the expression represent?

The total number of tasks Terrence completed
The total number of tasks Shelly completed
The sum of Shelly's and Terrence's total points