60 ← Amount she read
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100 ← Amount of pages there are
Find the lowest common factor.
In this case, we can say that it's 20. So, divide both the numerator and denominator by 20.
60 ÷ 20 3
--- = -------
100 ÷ 20 5
There is no other way to simplify this, so 3/5 is the most simplified version of 60/100.