To find the best estimate for the amount of money Megan has left after her purchases, first, we can round the amounts she spent and the amount she had initially:
- Megan's initial amount: $45.12 is approximately $45.
- Amount spent on lunch: $7.89 is approximately $8.
- Amount spent on sunglasses: $21.25 is approximately $21.
Now, we can subtract the rounded amounts:
Initial amount: $45
Total spent: $8 + $21 = $29
Now, subtract the total spent from the initial amount:
$45 - $29 = $16
So the best estimate for the amount of money Megan had left is approximately $16.