Help need help figuring out this problem

Ivan and jeff buy a package of 8 pens for $4.00. ivan wants 5 of the pens, and jeff wants 3.how much should each student pay?

Mikes car gets an average of 28 mpg. there are 12 gallons of fuel in mikes car when he starts his trip of 140 miles. about how many gallons are left at the end of his trip?

Jonathan puts $400 in a bank account. each year the account earns 6% simple interest. how much interest will be earned in 5 years?