B. 6 3/8
How do we get this? Simple:
6.375--->We already know that 6 will be the whole number in the mixed fraction.
We then move on to represent the decimal part as the fraction. 375 will be the numerator. The denominator depends on how many decimal places we have (3 in this case, since there are 3 numbers after the period--375). Each decimal place represents a 10 (or a 0 after the 1). So we get that our denominator will be a 1000.
We get the following fraction
6 375/1000
We simplify. Let's start by dividing numerator and denominator by 5:
6 75/200
Let's divide by 5 again:
6 15/40
Let's divide by 5 again:
6 3/8
Or we could have divide by 125 from the get go and get the same results.