3/8 is less than 3/4.
To find the answer, find the lowest common denominator.
To find the lowest common denominator, write down the multiples of 8 and 4.
$$8=8,16...
4 = 4, 8...$$
So, 8 is your lowest denominator.
Now, change 3/4 into 6/8 by multiplying 3/4 by 2.
Now, you can see that 3/4 is greater than 3/8.
You got your answer.