6 1/4
convert both mixed numbers into improper fractions:
multiply the denominator by the whole number and then add the numerator to convert into a improper fraction
4 3/4 = 18/4
1 3/4 = 7/4
then add the two numerators together
the denominator stays the same
18/4 + 7/4 = 25/4
then convert back into a mixed number:
find how many times 4 goes into 25; that's the whole number in your mixed fraction. The remainder is the numerator.
Since 4 goes into 25 6 times and has a remainder of 1, your answer is 6 1/4