In order to raise money, you are planning to work during the summer babysitting and cleaning houses. You earn $10 per hour while babysitting and $20...

In order to raise money, you are planning to work during the summer babysitting and cleaning houses.  You earn $10 per hour while babysitting and $20 per hour while cleaning houses.  You need to earn at least $1000 during the summer. 

a. Write an expression to represent the amount of money earned while babysitting.Be sure to choose a variable to represent the number of hours spent babysitting.

b. Write an expression to represent the amount of money earned while cleaning houses.

c. Write a mathematical model (inequality) representing the total amount of money earned over the summer from babysitting and cleaning houses.