计算,题目在下,快

﹙1﹚(2x²y+3x²y)-（6x²y-3x²﹚
=2x²y+3x²y-6x²y+3x²
=-x²y+3x²
﹙2﹚﹙5mn-2m+3n﹚+﹙-7m-7mn﹚
=5mn-2m+3n-7m-7mn
=-2mn-9m+3n
﹙3﹚﹙6a²-8a+11b³﹚-﹙11a²+2b³﹚
=6a²-8a+11b³-11a²-2b³
=-5a²-8a+9b³
﹙4﹚﹙2ab+3b²-5﹚﹣﹙3ab+3b²-8﹚
=2ab+3b²-5-3ab-3b²+8
=-ab+3