So,
x represents the number of bananas Tommy eats and y is the total number of pieces of fruit the monkey eats.
Translate the the second and third sentences in the question into mathematical form.
y = 4 (apples) + 2x (the number of bananas Tommy eats)
y = 2x + 4
This is actually slope intercept form, and it can be graphed.
Two points:
(0,4)
(1,6)