Ineed on this it’s about trig identities

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

If the ratio of sum of the first m and n terms of an ap is m2 : n2 , show that the ratio of its mth and nth terms is (2m − 1) : (2n − 1).

Megan is making bracelets to sell to earn money for the local animal shelter. it takes her 1/4 hour to pick out all the beads and 1/10 hour to string them.this week, she only has 5 1/4 hours to make bracelets. how many bracelets will megan be able to make?