One idea is:
Paul wants to buy an iphone X. He has savings of $100 to start with. Local McDonalds pays $7 per hour (after tax) to students on summer break for helping out at the counter. The iphone costs $1000. At least how many hours does Paul need to work at McDonalds to be able to afford the iphone.
So, that matches ax+b>c in that
a is the hourly earning
b is the initial savings
c is the price of the iphone
