Question

Emilio owns a bakery. The number of boxes of cookies he has left on a Monday is represented by the function x + y = 42, where y is the number of boxes of cookies remaining in the bakery and x is the number of hours since he opened the bakery. How many boxes did he have at the start of business on Monday? (Note: x ≥ 0, y ≥ 0, and y takes only integer values.)

Answer 1

Emilio is going to have 42 boxes at the start of Monday. 
x=the number of hours his store has been open, but it's the beginning of the day and his shop just opened so x will be = to 0. 
y= the number of boxes

well if we plug in what we have it reads
0+y=42
if we subtract 0 from both sides we get y=42. So Emilio has 42 boxes