(1) 由2x+3y=18-n,4x-y=5n+1,化简,得y=5-n,x=n+1.5,则x-y=2n-3.5=0.1,则n=1.8.
(2)y=5-n,x=n+1.5,又因为y+n>x,则5>n+1.5,即n<3.5,x+n>y,则2n+1.5>5-n,即n>1.17,n为正整数,所以n=2或3.即三角形2,3,3.5,或3,2,4.5.所以存在