Let g= geese
b = buffalo
geese have 2 legs and buffalo have 4 legs
g+b = 15 the total number of animals
2g +4b = 56 the total number of legs
Multiply the first equation by -2
-2g -2b = -30
Add the second equation to eliminate g
-2g -2b = -30
2g +4b = 56
--------------------
2b = 26
Divide by 2
2b/2 = 26/2
b = 13
There are 13 buffalo
g+b = 15
g+13 = 15
g =2
There are 2 geese and 13 buffalo