2/5x÷3/4=8/72/5x=8/7×3/42/5x=6/7x=6/7÷2/5x=6/7×5/2x=15/7
解2/5x÷3/4=8/72/5x4/3x=8/78/15x=8/7x=8/7x15/8x=15/7