The y intercept will be 5
Marbles in a bag: 3 green, 4 yellow, 5 blue, 8 pink.
Event A - get a green or yellow marble
Event B - get a pink marble
Events A and B are independent because we draw a marble from a bag with 20 marbles in both cases.

Probability of combined events is
50$ per month for 12 years would mean she spent only (50 x 12) 600$ per year.
She actually spent $711, her forecast was off target by (600-7111) $111.
She exceeded her budget by $111