One helpful technique I used to stay focused is to buy a pack of m&ms or mini candies and every time I complete a problem I eat one candy or m&m. Also, try making a goal for yourself for example "my goal is to complete 100 problems in an hour"
$0.30x=y should be the answer because there is a 30cent fee for every day and x represents how many days it's kept therefore you would add 30 cents for every day it's kept so it's valid to say $0.30x=y becaue the 30 cents times the total of days it's kept = y (the toatl)
