Answer:
He needs to sell 100 souvenirs
Step-by-step explanation:
We want to know the number of souveniers John has to sell
Let the number of souveniers he sold at the game be s
At a rate of $0.25 per souvenier, the amount earned on souveniers for s souveniers will be:

Now, if we added this to the amount he earns per game, we will have the total $35 earned for working at one game.
Thus, mathematically:
