化简并求值:2m-{n+[4n-3(m+2n)+6m]-5n},其中m=2/3,n=4

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化简并求值:2m-{n+[4n-3(m+2n)+6m]-5n},其中m=2/3,n=4

2m-{n+[4n-3(m+2n)+6m]-5n}
=2m-{n+[4n-3m-6n+6m]-5n}
=2m-{n+3m-2n-5n}
=2m-{3m-6n}
=2m-3m+6n
=-m+6n
=-2/3+6*4
=23又1/3