using simultaneous equations solve these problemsa)  A moneybox contains only 20-cent coins and 50-cent coins. If there are57 coins in the moneybox and their total value is $24.30, how many 20-cent coins and how many 50-cent coins are there?b) Twelve years ago Jack was five times as old as Jill. In 3 years’ timeJill will be half of Jack’s age. What are Jack and Jill’s present ages?