Answer:
The value of x = 3
Explanation:
In ΔRTS
Exterior Angle theorem: An Exterior angle of a triangle is equal to the sum of the opposite interior angles.
In the given triangle RST,
is the exterior angle of the triangle RTS
and
and
are the two opposite interior angles.
Therefore, by the definition of Exterior Angle theorem;

Then;

Combine like terms,
9x = 6x+9
Subtract 6x from both the sides we get;
9x - 6x = 6x+9-6x
Simplify:
3x = 9
Divide by 3 we get;

Simplify:
x= 3