f(x) as a linear equation:
gradient = (12-4)/(4-2) = 4
y - 4 = 4(x - 2)
y = 4x - 4
Therefore f(x) = 4x - 4
g(x) = 10x - 4
Since it already started at 10 and it increases by one every level (x):
h(x) = x + 10
Therefore, since g(x) has the largest gradient (10x), it has the largest slope