André gets paid $5 a week for his allowance and $10 every time he mows his neighbor's yard. He puts all his
money into his piggy bank. His piggy bank contains $70 and has only $5 bills and $10 bills. He also knows he
has 11 total bills in the bank. How many of each type of bill does André have in the bank?
There are actually two equations in this problem using the same variables. This leads to a system of
equations you need to solve.

1. Write an equation that represents the total value in his piggy bank.
2. Write an equation that represents the total number of bills in his bank.
3. What do you notice about the variables in these two equations?.