18 animals in a pet store. some are birds and some are dogs. there are 50 legs in all. how many birds and how many dogs are there

A bird has only 2 legs, and a dog has 4 legs.

x=number of birds

y=number of dogs

We can susggest this system of equations:

x+y=18

2x+4y=50

We can solve this system of equations by substitution method.

x+y=18 ⇒ y=18-x

2x+4 (18-x) = 50

2x+72-4x=50

-2x=50-72

-2x=-22

x=-22/-2

x=11

y=18-x

y=18-11

y=7

Answer: we have 11 birds and 7 dogs.