As a salesperson, you are paid $50 per week plus $3 per sale. this week you want your pay to be at least $110. what is the minimum number of sales you must make to earn at least $110?

Your answer is $60. how i got this by taking 3 and multiplyed it by $20 and that gave me $60. so we know 60 + 50=110 so it's the same as $60 + $50=$110. 
also you could put it in a equation which is $50 + $3(x)=$110. 
to solve that you would just find out what can fit in the X place which was $20.

=>so this is your answer, $20.00. <=