In this question the most important thing is to know the conversion between kilometer and meter. Once that is known the problem becomes very easy to solve.It is already given in the question that 3/4 of 1 kilometer has to be determined in the unit meter.
So
1 kilometer = 1000 meter
Then
3/4 of 1 kilometer = (3/4) * 1000 meter
= 3 * 250 meter
= 750 meter
So from the above deduction, we can see that 3/4 of 1 kilometer is equal to 750 meter. I hope the procedure for getting to the answer is easy enough for you to understand.