Vectors can slide along the axis they are in for the purpose of calculating moments. So, we can slide the X component of the force acting at C until it makes a perpendicular angle to the moment arm from point A. After we move this vector, the moment arm will only be 1.5m*Sine(30).
howcome you didnt add 3 meters to the x component when you were doing the moment, but you did it for y ?
Vectors can slide along the axis they are in for the purpose of calculating moments. So, we can slide the X component of the force acting at C until it makes a perpendicular angle to the moment arm from point A. After we move this vector, the moment arm will only be 1.5m*Sine(30).