You buy a package of 12 pencils for $2.64 write this rate as a unit rate?

What is the size of the matrix resulting from

Carlos spent 1 1/4 hours doing his math homework he spent 1/4 of his time practicing his multiplication facts how many hours to carlos been practicing his multiplication facts

1) prove that 731^3−631^3 is divisible by 100 2) prove that 99^3−74^3 is divisible by 25