If the world record for swimming the 50 meter frestyle event was 21.34 seconds. suppose the athlete swam at a constant rate, what was his speed?

Speed = distance/time Which in your case means 50 meters/ 21.34 seconds, which equals 2.343 meters per second.

the law of definite proportions states samples of a compound will always contain the same proportion of elements by mass. in other words, a given compound will always contain the same elements in the same proportions by mass.the law of multiple proportions states when two elements combine with each other to form more than one compound, then the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.