解（-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn）=-2mn+2m+3n-3mn-2n+2m-m-4n-mn
=-2mn-3mn-mn+2m+2m-m+3n-2n-4n
=-6mn+3m-3n
=-6*2+3（m-n）
=-12+3*4
=0