Two congruent right triangles with sides of 3, 4, 5 are placed together so that one pair of corresponding sides touch and the resulting figure is another triangle. What would be the perimeter of the resulting triangle?

It depends on which pair of the sides are touched ... if the 4s are touched then the perimeter would be 5+5+3+3=16, if the 3s are touched then the perimeter would be 5+5+4+4=18 but if the 5s are touched then it becomes a rectangle so that's irrelevant