Math help please now

If you have 12 feet of string and you cut it into equal length of 5 inches each how much string will be left

Find the maximum value of p= 4x + 5y subject to the following constraints :

Sophia wrote an equation to represent the revenue of a movie theater for one day. she let x represent the number of child tickets sold and y represents the nunver of adult tickets sold. if a child ticket cost $4, an adult ticket cost $6, and the total revenue for the daybwas $420, which equation could sophia use to represent the number of chikd and adult tickets that were sold?