Hello, smiler!

I'm sure you know enough of the basic to solve this.

You just have to put it all together . . .

The line through the origin is normal to the plane

Find the point in which meets the plane

The plane has the normal vector: .

This is the direction vector of the line through the origin.

Its equations are: . .[1]

To find its intersection with the plane: . .[2]

. . substitute [1] into [2]: .

Substitute into [1] and we have: .