The measures of two of the sides of an equilateral triangle are 3x + 15 in. and 7x - 5 in. What is the measure of the third side in inches?

It has to be first understood that this is an equilateral triangle and so all sides of the triangle are equal. Now let us focus on the two sides already given in the question.

3x + 15 = 7x - 5

3x - 7x = - 5 - 15

- 4x = - 20

4x = 20

x = 20/4

= 5 inches

So the length of all three sides of the equilateral triangle is 5 inches. I hope the procedure is clear enough for you to understand.