4 5/12-1 1/2:(2 1/6+8/15)*1 4/5=

2 1/6 + 8/15 = 2 5/30 + 16/30 = 2 21/30 = 2 7/10 1 1/2 / 2 7/10   3/2  / 27/10 = 5/9 5/9 *  1 4/5  = 5/9  * 9/5 = 1 4 5/12 - 1 = 3 5/12