Explanation
A function is defined as a relation between a set of inputs having one output each,in this case our independent variable is the number of days( d) and the dependent variable would be the number of pizzas
so
Step 1
let the function
therefore, to know the number of pizzas are in the stock after 5 days we need to evaluate the equation for d=3
so
so, after five day there willbe 28 pizzas in stock
I hope this helpsyou