都乘以30 6x+10x=13 16x=13 x=13/16 =6/17×1/8+1/8×11/17 =（6/17+11/17）×1/8 =1×1/8 =1/8 =1/5×30+3/5×30-1/6×30 =6+18-5 =19 =1/2+（1/3×5/2-1/3） =1/2+（5/2-1）×1/3 =1/2+3/2×1/3 =1/2+1/2 =1
