Answer:
x = 2
Explanation:
Since the triangle is equilateral, all the sides will be that same length.
That would mean 10x - 5 = 6x + 3
Then you can simplify the expression down to get x.
10x - 5 = 6x + 3 (add five to the other side)
10x = 6x + 8 (subtract 6x)
4x = 8 (divide)
x = 2