These math problems might go right up your alley

Okay so here it goes,

I am very upset not to mention confused over how to do consumer Math. I will post some of the ones I got wrong here. My hope is that someone will show me how to do the work so that I may understand how it is done. Please help me if you can.

Fran brings home $225 per week working 15 hours of which she is able to save $40. Fran wants to have $1400 saved at the end of 20 weeks She May work up to 18 hours per week if she wants. She can save all of the money earned working the extra hours.

Answer is : Fran must work at least 17 hours per week to meet her goal.