They don't.
three eighths
No it is not. 5 and 3 eighths are bigger by one eighth.
five eighteenths
the answer is five eighths.
7/8
One fourth is considerably less than five eighths. To convert fourths into eighths, you can multiply the fraction 1/4 by 2/2 and get 2/8. It should be apparent that two eighths is a lot less than five eighths. Less than half, in fact.
five eighths
yes yes it it
No. 1/4 = 2/8.
1
one eighth two eighths make one fourth
3 and 3/8