You multiply 8 x 3/4=24/4. Then you simplify your answer and it is 6 hours. 24/4 is division 24 divided by 4 equals 6.
Or, you can change 3/4 to a decimal which is .75. Then you multiply .75 x 8 and the answer is 6.00 which is 6 hours because you do not use the zeros after the decimal point.