Practically, if the nominator has a common factor with the denominator of the other fraction is can cancel out. For example. If u have the fractions 3/4 and 8/9, 3 and 9 have a common factor which is 3. So 3 goes into 9 3 times and 3 goes into 3, 1 time so the three becomes a 1 and the 9 becomes a 3. Same with the 4 and 8. They have a common factor of 4 (it can also be 2) 4 goes into4 one time (think of is a division), 4 divided by 4 is 1, 8 divided by 4 is two. So 4 goes into 8 2 times. So now it’d be easier to multiply. So it’d be 1/1 x 2/3 so now u just multiply across which would just equal 2/3.