Not sure what you mean by a fraction bar but the answer is 10/12*6/4:
10*6 =
12*4
5*1 =
2*2
5
4
The answer is 5/4 or 1 1/4. See how 6 is divided into 12 leaving 2 in the denominator. 10/4 reduces to 5/2 because 2 is a common factor which cancels out. That just leaves 5 in the numerator and 4 in the denominator.