the perimeter of the triangle, namely the sum of all its 3 sides, is 110.
now, the three sides are in a 6:7:9 ratio, namely, if we divide 110 by (6+7+9), it will give us hmmm 110/22, a quotient of 22 equal pieces, namely how many times 22 would go into 110.
now, the small side, takes 6 of those pieces, the medium side takes 7 of them and the largest takes 9 of those pieces.
110/22 = 5
the small side is then 6(5).
the medium side is 7(5).
and the largest side is 9(5).
add them up, and you'd get the perimeter, 110 inches.