$70 is what he would have left. Since each trip is $14 you would multiply that by the amount of times he went which was 11. 14x11 is $154. But you need what he has left so you take his total amount $224-$154 and get $70.
Part b.) 16 times. He has $224 total. You want to find out how many times he can go on the tool roads. We know the toll roads cost $14 each time. So you do $224/14 and get an even amount of 16. He would be able to use it 16 times before he have no money left.
