Answer :
turtles=x
frogs=x+4
crayfish=3+2x
54=x+(3+2x)
54=3+3x
51=3x
x=17
frogs=x+4
=17+4
There were 21 frogs
frogs=x+4
crayfish=3+2x
54=x+(3+2x)
54=3+3x
51=3x
x=17
frogs=x+4
=17+4
There were 21 frogs