Knowing the total number of heads and feet, find the number of chickens and rabbits, (total number of feet-number of feet per chicken × total number of heads) ÷ (number of feet per rabbit-number of feet per chicken) = number of rabbits, total number of heads-number of rabbits = number of chickens. Or (number of feet per rabbit × total number of heads-total number of feet) ÷ (number of feet per rabbit-number of feet per chicken) = number of chickens, total number of heads-number of chickens = number of rabbits.

Formula 1 (number of rabbit feet × total feet-total feet) ÷ (number of rabbit feet-number of chicken feet) = number of chicken feet. Total number-number of chickens = number of rabbits. Corresponding binary equation operation: (s 1*4-s2)/2.