Verified answer

When two lines intersect, the x values are equal, as are the y vlaues and z values. So set the y values equal, and solve for s. 1 = 5 -4s and so s = 1. Now use that in the x equation. 5 + 5t = 1 + 4s. Use s = 1 and it follows that t = 0. Now just plug in those values to all 6 of the coordinates.

Now I can help you:

5+5t=1+4s

1=5-4s

4+2t=-1+5s.

Solving the equations you get s=1 & t= -1/2 and t=0, but this doesn't satisfy the three equations, since t has 2 values so the two lines don't intersect.

I hope this helps.