2/5m + 3/10m- 2/15m=1/6
2/5m+3/10m-2/15m=1/6 12/30m+9/30m-4/30m=1/6 21/30m-4/30m=1/6 17/30m=1/6 m=1/6:17/30 m=5/17
M * (2/5 + 3/10 - 2/15) = 1/6, m * (12/30 + 9/30 - 4/30) = 5/30, m * 17/30 = 5/30, m = 5/30 : 17/30, m = 5/30 * 30/17, m = 5/17