Answer:
4.5 in, 6 in, 7.5 in
Step-by-step explanation:
The sum of the ratio units is 3+4+5 = 12. These correspond to 18 inches, so each ratio units stands for (18 in)/12 = 1.5 in.
The side lengths are ...
3×1.5 in = 4.5 in
4×1.5 in = 6.0 in
5×1.5 in = 7.5 in
