Let the number of chickens = c.Let the number of pigs = p.A chicken has 1 head and 2 legs. c number of chickens have c heads and 2c legs.A pig has 1 head and 4 legs.p number of pigs have p heads and 4p legs.There are 40 heads.Equation for heads:c + p = 40There are 110 legs.Equation for legs:2c + 4p = 110System of equations:c + p = 402c + 4p = 110Solve the first equation of the system of equations for c:c = 40 - pSubstitute 40 - p for c in the second equation:2c + 4p = 1102(40 - p) + 4p = 11080 - 2p + 4p = 11080 + 2p = 1102p = 30p = 15Now substitute p = 15 in the first equation to find c.c + p = 40c + 15 = 40c = 25There are 25 chickens and 15 pigs.