Lemma get some help plz

Jenisey has $24 to spend on seven pencils. after buying them she had $10. how much did each pencil cost.?

If g^-1(x) is the inverse of g (x) which statement must be true

The sum of the speeds of two trains is 720.2 mph. if the speed of the first train is 7.8 mph faster than the second train, find the speeds of each.