You're going to want to take the total, which is $353.00 and subtract the initial cost, which is $84.00, the number now should be $269. Using that total divide it by $68.00, there you should find your answer of about 4 hours. The precise answer is 3.99588235. But you would round that to 4 hours.
It would be letter. b....
D. Because you're multiplying 3 by a number which is what the variable represents (n), then you're just adding 7 to that which equals 19 all together. It all translates to 3n+7=19.