Final answer:
25% of Laura's exercise time was spent on walking.
Step-by-step explanation:
To find the percent of Laura's exercise time spent on walking, we need to calculate the ratio of the time spent walking to the total exercise time, and then multiply by 100 to convert it to a percentage.
Total exercise time = 115 + 50 + 75 + 80
= 320 minutes
Percentage spent on walking = (Time spent walking / Total exercise time) * 100
= (80 / 320) * 100
= 25%
Therefore, 25% of Laura's exercise time was spent on walking.