Tony is driving a truck of mass 2.00 × 103 kilograms to the west with a velocity of 14.0 meters/second. he collides with a car of mass 1.20 × 103 kilograms moving to the south with velocity 21.0 meters/second. after the collision, they move together. find the velocity with which they move together

You would multiply the 2 and the 103 together to have one number to work with rather than one equation to make up another equation. You would do the same with 1.2 and 103. Multiply the results with their velocity (206 and 123.6), like so. 206*14 and 123.6*21. From this u would get 2884 and 2595.6. Add them together and divide that answer by three. {The answer should be 2739.8.}