The value of x in the similar triangles is determined as 15. (Option C).
How to calculate the value of x?
The value of x in the similar triangles is calculated by applying the following formula as shown below;
Using the principle of proportion of the side lengths of the triangle, we will have;
(x - 6)/3 = x / 5
5(x - 6) = 3x
Simplify the expression to obtain the value of x as follows;
5x - 30 = 3x
5x - 3x = 30
2x = 30
divide both sides by 2
2x/2 = 30 / 2
x = 15
Thus, the value of x in the similar triangles is determined as 15.