There is no age to learn and teach. You are great Teacher/MentorThis is a young student who seems to be struggling in math. I will give a hand with this problem.
First let's motivate subtraction. If 7 bars of chocolate were purchased and Hina ate 2 bars and Arman ate 5 bars than Arman ate how much more than Hina? The result is 5bars - 2bars = 3bars. We subtract.
Now if you read 3 pages in you math book every 4 minutes, then how many pages do you read in 8 minutes? Since 8 = 4+4 and every 4 minutes you read 3 pages then you read 6 pages every 8 minutes.
This means that 3/4 = 6/ 8. Think of 6/8 as 6 out of 8. Since 6 out of 8 is more than 1 out of 8 we have that 3/4=6/8 is more that 1/8
Now that we know which is bigger we can subtract (larger - smaller) and get that 3/4 - 1/8 = 6/8 - 1/8 = 5/8. So Arman ate 5/8 more of the bar than Hina