1-1/3 = 2/3 1-3/5 = 2/5
原方程化为
2/3 x + x + 2/5 x = 31
通分 10/15 x + 15/15 x + 6/15 x = 31
31/15 x = 31
两边乘以15
31x = 31 * 15
x = 15