we are going to create a table in excel and we will assign different values of topping to know when the price is equal in both pizzerias
  
 see the attached figure
  
 the answer is
 5 toppings from palanzio’s pizzeria
 6 toppings from guido’s pizza
cost palanzio’s pizzeria----> 6.80+0.90*5-----> $11.30
cost guido’s pizza------> 7.40+0.65*6----------> $11.30