Final answer:
The equation to represent Mu's charity lap-walking where her sponsors donate $7 per lap and Mu has raised $105 in total is 7 × l = 105, where l is the number of laps. Dividing both sides by 7 gives us l = 15, therefore, Mu walked 15 laps.
Step-by-step explanation:
To write an equation that describes Mu's charity lap-walking situation, let's use the variable l to represent the number of laps Mu walks. For each lap, the sponsors donate $7, so we can say that the total amount of money raised, which is $105, is equal to 7 times the number of laps. Therefore, the equation to describe this situation is:
7 × l = 105
Where l is the number of laps. To find out how many laps she walked, we can solve for l by dividing both sides of the equation by 7:
l = 105 ÷ 7
After performing the division, we find that:
l = 15
So, Mu walked 15 laps to raise $105 for charity.