Question

What is a real world situation for 15 +c= 17.50

Answer 1

All you need to do is make c =  2.50.

Mike has 15 dollars in his pockets when he started his walk, and when returned home his pockets now had $17.50. How much money did Mike pick up on the walk?

Mike is buying $17.50 worth of items from the store. He only has $15 with him, how much more does he need?

Hope this helps!

Answer 2

We could use this equation like this:
I spent 17.50 on two articles at the store, one of the articles cost me 15, how much did the other article (c) cost?
Then we have the equation:
15 + c = 17.50
Where we are adding the articles bought, equal to  the total spent, we solve for c:
c = 17.50 - 15
c = 2.5
Then the unknown article costs 2.5 and then all the variables are known in the problem.