Firstly, you must find the product of 2 and x which is 2x. Add 8 and you get 2x+8.
Answer:

Step-by-step explanation:
Slope-intercept form: y = mx + b
The line intersect Y-axis at y=0 so b = 0
The line passses through points (0, 0) and (2, -1), so the slope:

Therefore the equation:

R would equal -189, there is step by step in the picture
Average is
(2x + X+6)/3=63
(2x+x+6)= 189
3x+6=189
3x=183 61
X=61
Scores for the game are: 61, 61, and 67