This is a good question and I can see your confusion. Fractions can be tricky at times, especially when whole numbers and fractions are combined. The best way to think about this is to separate the whole number from the fraction. When you do this, you have 6 and 1/4.

At this point, you would want to make the fraction into a decimal. When you do this 1/4 translates into .25. In short, you have a quarter of some unit.

Finally, you put it all together and you have an answer of 6.25. The key point is to rememeber to break things down into managable parts. By doing so, you can simplify almost any math problem.