Why is it so many numbers

The reaction q+r2=r2q is found to be first order in r2 and

V1t2 = v2t1 is an expression of who’s law

Three cards with holes are arranged in a straight line. a light is shined through the first card’s hole and travels through all three cards. what does this tell you about light rays? a) that light is reflected b) that light is refractive c) that light travels in a straight line d) that light does not travel in a straight line