here's a hard one 3D vectors

[james cook]

these are the position vectors and velocites of 2 missiles

rA=600i
rB=2200i=4000j+600k
vA=-196i+213j+18k
vB=-240i+100j

A and B do not intercept find how much they miss by
and how much must A change its velocity in order to intercept.

 

[jimi]

if rB=2200i=4000j+600k should be rB=2200i+4000j+600k then I make it about 55.
As far as I can see your second problem has infinite solutions.