Answer:d
Explanation:
Given
Shelly completed x tasks and scored 90 points on each one
Therefore total points scored by Shelly is 90 x
The expression shows the total point scored by Terrence in game is
90x-20
Thus difference between their Points are 90x-(90x-20)=20
So constant 20 show the difference between Shelly's and Terrence's total Points.