Fractions can be simplified by making sure that the numerator and the denominator cannot be divided by any number.
The given 12/60 is very obvious that it is divisible by 2.
After dividing by 2, you will get 6/30.
It seems it is not in simplest form. It is divisible by 3.
Dividing the numerator and denominator by 3 then you will get
2/15.
So the lowest term is 2/15.