672
1)15x/20y=3x/4y
2) 6xy/8y^2=3x/4y
3) 2m^2/3mn=2m/3n
4)24a^3/56a^2b=8a/14ab
673
1) 8x-3=5x+3
8x-5x=3+3
3x=6
x=2
2)x-7+8x=9x-3-4x
9x-5x=-3+7
4x=4
x=1
674
1) (x^2-9)/(x+3)=(x-3)(x+3)/(x+3)=x-3
2)(a-b)^2/)a^2-b^2)=(a-b)^2/(a-b)(a+b)=a-b/(a+b)
3)(25-x^2)/(x+5)=(5-x)(5+x)/(x+5)=5-x