Answers

2014-08-17T18:34:32+08:00
-{4y-[13x-(14y-2x)]-18y}

= -[4y-(13x-14y+2x)-18y]

= -[4y-(15x-14y)-18y]

= -(4y-15x+14y-18y)

= -(-15x) = 15x


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