Based on the change in the perimeter, the scale factor of the dilation is 3.5.
The scale factor of the dilation refers to the number of times the triangle was dilated such that it went from 12 inches to 42 inches.
This dilation can be found as:
= Increased perimeter / Original perimeter
Solving for it would give:
= 42 / 12
= 3.5
In conclusion, the scale factor of the dilation is 3.5.
Find out more at https://brainly.com/question/8765466.
