Y = 4 - x
3x + 4(4-x) = 14
3x + 16 -4x = 14
-x = -2
x = 2
y = 2
Your taking off $20 from the amount that you have to begin with
The acceleration is given by the slope of the line. This line passes through the points (0, 2) and (3, 5), so it has slope

which means the acceleration over this 3 second interval is 1 m/s^2.