if we let that V_gp be the vocabulary {+,0} where + is abinary function and 0 is a constant . we use the notation x+y to denote the term +(x,y) . Let gama be the conjunction of the following V-sentence: for all x the exist y for all z (x+(y+z)=(x+y)+z)

for all x (( x+0=x) conjunction ( o+x=x))

for all x ( there exists y (x+y=0) conjunction the exist z (z+x=0))

how can I give a model of gama that does not model the sentence for all x for all y((x+y)=(y+x)).