Answer: 7 47/63
Step-by-step explanation: First, find the common denominator of 6/7 and 8/9. You can do this by writing out the multiples of each denominator:
7 14 21 28 35 42 49 56 63
9 18 27 36 45 54 63
The first number at which they match is the common denominator. Next, find the sum of the numerators relative to this new denominator:
6/7 * 63 = 54
8/9 * 63 = 56
Finally, add the numerators, simplify the improper fraction, and add that to the sum of the original whole numbers:
(54 + 56)/63 = 110/63 = 1 47/63
(4 + 2) + 1 47/63 = 7 47/63