Answer:
Daria bought 11 refills of lemonade last month
Step-by-step explanation:
The equation is:
y = 2x + 9
The cup costs 9 dollars and is 2 dollars per refill
She spent 31 dollars so:
31 = 2x +9
Now we can solve!
2x + 9 = 31
Subtract 9 from both sides!
2x = 22
Divide both sides by 2!
x = 11
We know x is the amount of refills so,
Daria bought 11 refills of lemonade last month!
