Let's first turn all the words into numbers:
Two and four tenths = 2.4
One and six tenths = 1.6
Four and one tenth = 4.1
Now lets represent "a number" as x.
Then translate the wording into a linear equation:

Simplify and isolate the variable:

Divide by 0.8
x>1.375 or x>1 3/8
Answer:
4
Step-by-step explanation:
You were on the right track.
210 - 48 = 162
162/3 = 54 dimes
15/20
Figure out what number to use for simplify
Which is 5
Divide the numerator and denominator by 5
15/5=3
20/5=4
Answer:3/4