First you need to get the GCF of the numerator and the denominator
GCF or Greatest Common Factor means getting the highest number that divides exactly into two or more numbers except for 1.
In this case 8 have a factors of 2, 4, and 8 while 12 have 2, 4, 6, and 12.
Next find the highest GCF of both that matches.
So that will be 4
Next divide that number to the numerator and denominator of the fraction
That will like this:
8 / 4 = 2
12 / 4 = 3
Therefore we have
2/3 as the lowest term of 8/12
I hope that helps