You have 38 animals with a total of 68 legs. some have 2 legs and some have 4. what is the equation you use to work out how many 2 legged and 4 legged animals there are?

X = nr. of animals with 2 legs ;
y = nr. of animals with 4 legs;
We have x+ y = 38 and 2x + 4y = 68 ;
Then x = 38 - y ;
2( 38 - y) + 4y = 68 ;
76 - 2y + 4y = 68 ;
2y = - 8 ;
y = - 4 False, because y > 0 ;