i will start you off. note that the normal vector to the plane is <1,2,3> (you see that, right?). since the normal vector is perpendicular to the plane, we can use this vector as the direction vector for our line.

so what you want is the line passing through (1,1,-1) with direction vector <1,2,3>

can you finish? (there is a formula in your text that tells you how to get the line from that information)