（1）3a/4b乘16b/9a²,
=4/3a
（2）12xy/5a÷8x²y,
=3x/10a
（3）（-3xy）÷2y²/3x,
=-3xy×3x/2y²
=-9x²/y
（4）x+y/x-y乘y-x/x+y,
=-1
（5）3a-3b/10ab乘25a²b³/a²-b²,
=3(a-b)/2×5ab²/(a+b)(a-b)
=15ab²/2(a+b)
（6）4y²-x²/x²+2xy+y²÷x-2y/2x²+2xy
=(2y+x)(2y-x)/(x+y)²×2x(x+y)/(x-2y)
=-(2y+x)·2x/(x+y)
=-2x(x+2y)/(x+y)