The store owner is adding cost, so we will use addition. The answers should be as follows:
[] c + $3.49 = $9.84
[] c = $6.35 <- subtract $3.49 from both sides of the equation
[] Solution of answer represents the old cost of the toy.
Have a nice day!
I hope this is what you are looking for, but if not - comment! I will edit and update my answer accordingly. (ノ^∇^)
- Heather