Final answer:
Mia will need 9 weeks to save up the $28 she needs.
Step-by-step explanation:
To find out how long it will take for Mia to save up the $28 she needs, we can set up an equation. Let x represent the number of weeks it will take Mia to save up the money. We know that Mia has $10 saved so far and she can save $2 from her allowance each week. So, the equation is: 10 + 2x = 28. Now we can solve for x. Subtract 10 from both sides of the equation: 2x = 18. Divide both sides by 2: x = 9. It will take Mia 9 weeks to save up the $28 she needs.