ho wto solve questions based on the fact that only quantities can be added or subtracted

Two physical quantities can be added or subtracted if they have the same dimensions/units.

So you can add, let two velocities initial and final.

If you want to add constant acceleration to a initial velocity,

you have to multiply acceleration by the given time, so that acceleration x time = velocity, which you can add to initial velocity.

Please submit specific problem for further illustration.

Regards,

Team,

TopperLearning.