Answer- C. For every extra person served, the time it takes to prepare a meal increases by 7 minutes.
Solution-
y = 7x+25
Where y = the number of minutes it takes to prepare a meal
x = the number of people being served.
If the number of persons increased by one, so x' = (x+1)
Then y' = 7x' + 25 = 7(x+1) + 25 = 7x + 7 + 25 = 7x + 25 + 7 = y + 7
∴ As y gets increased by 7 for every 1 more person , so C is the correct answer.