42 inch
The perimeter of the ratio triangle is 6+4+3=13
Divide that into the actual triangle perimeter to get the scale 91/13=7
Multiply that scale times the longest side of the ratio (6)
7x6 = 42
To check do the other two as well
7x3=21 and 7x4=28
Add them up to check the perimeter
42+21+28=91
And 42 was the longest side
