先把代数式（5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)化简
（5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)
=5XY+4X+7Y+6X-3XY-4XY+3Y
=-2XY+10X+10Y
=-2XY+10(X+Y)
当X+Y=6,XY=3时
原式=-2*3+10*6
=-6+60
=54