To find the cost of a large pizza with 3 additional toppings using the function \( y = 11 + 1.5x \), where \( x \) represents the number of additional toppings:
- Substitute \( x = 3 \) into the equation:
\[ y = 11 + 1.5(3) \]
- Calculate the additional cost for the toppings:
\[ y = 11 + 4.5 \]
- Add the costs together:
\[ y = 15.5 \]
Thus, the cost of a large pizza with 3 toppings is $15.50.