David loves to cook! He knew 21 recipes before starting cooking school and he learns 2 recipes every 1 one week. An equation to represent that is y = 21 + 2x where x represents number of
weeks and y represents number of recipes.
His friend Sarah believes that if he attends school for 10 weeks that means he knows 42 recipes.
Explain if she is correct.

Sarah is not correct because if David already knows 21 recipes and learns 2 recipes per week, then he will know only 41 recipes after 10 weeks, not 42.

Step-by-step explanation:

To see if Sarah is correct, let's replace the y in the equation with 42 and the x with 10:

y = 2x + 21

42 = 2(10) + 21

42 = 20 + 21

42 41

Sarah is wrong.

it would take 7/10 of an hour too fill the pool.

step-by-step explanation:

-2x + 7 = 7

subtract 7 from both sides.

-2x = 0

divide both sides by -2.

x = 0