?? Vectors are "free floating"- only specific representations have initial points. And even those may not intersect- they may not reach far enough.
If you mean you have two lines, one passing through [itex](x_0,y_0,z_0)[/itex] in the same direction as vector Ai+ Bj+ Ck, the other passing through [itex](x_1, y_1, z_1)[/itex], in the same direction as vector Ui+ Vj+ Wk, then the first line can be written in parametric equations [itex]x= x_0+ At[/itex], [itex]y= y_0+ Bt[/itex], [itex]z= z_0+ Ct[/itex] and the second line can be written in parametric equations [itex]x= x_1+ Ut[/itex], [itex]y= y_1+ Vt[/itex], [itex]z= z_1+ Wt[/itex]. Set "x=x", "y= y", "z= z", and solve the resulting three equations for s and t.
Of course, in general, three equations won't give just two unknown values- in three dimensions most lines are "skew" and don't intersect. If you are working in 2-dimensions, (x, y), just ignore the z equations and you have two equations to solve for s and t.