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;