Given :cos x = 5/8
we know that,
in a dilatation the angles do not change
example
in a right triangle
cos x = Adjacent side angle x/Hypotenuse
So,
When the triangle is dilated by 3
the adjacent side will be dilated to 15 and the Hypotenuse will be dilated to 24
which means 5/8 will become 15/24
and hence,
15/24 after simplifying will be 5/8.
Thus there is no change
the answer is the option
5/8
