$\frac{32x50}{48x75}$=$\frac{4x1}{3x3}$=$\frac{4}{9}$(triệt tiêu những số chia hết)
$\frac{63x81}{135x84}$=$\frac{3x3}{5x4}$=$\frac{9}{20}$
$\frac{3x145+3x55}{6x215+6x85}$=$\frac{3x(145+55)}{6x(215+85)}$=$\frac{3x200}{6x300}$=$\frac{1x1}{3x1}$=$\frac{1}{3}$