7/8 Because there are (7 marbles that are not 8 / 8 possibilities).
If the slope of the function is 2, the amount it can change over the interval 0–2 is
... 2×2 = 4 units
If the slope is 7, the amount it can change over the interval 0–2 is
... 2×7 = 14 units
The least possible value of f(2) is 2+4 = 6.
The greatest possible value of f(2) is 2+14 = 16.