Final answer:
Mary climbed higher up the rock wall compared to Vincent.
Step-by-step explanation:
To compare how high Mary and Vincent climbed up the rock wall, we need to find a common unit of measurement. Let's convert the fractions to the same denominator. The least common denominator for 4 and 8 is 8. So, we can rewrite 3/4 as 6/8 and 3/8 remains the same. Comparing the two fractions, we can see that 6/8 is greater than 3/8. Therefore, Mary climbed higher up the rock wall compared to Vincent.