To solve this problem, let's first write out Joseph's equation in words. This is:
Cost = (cost of each topping)X(number of toppings) + cost of food item.
Now that we have figured this out, we can look at Hattie's stand. The problem tells us that cost of each topping is $0.25, and the hamburger is $2.50. The number of toppings will be represented by x. Now, we substitute in Hattie's costs into the equation.
C = 0.25 [cost of each topping]x + 2.50 [cost of hamburger]
Without these words, the equation is: C = 0.25x + 2.50