помогите решить пример. (5/6-3/10):(3/10+2/15)

      1         3         2
(5/6 - 3/10) : (3/10 + 2/15) = 1 3/13
1) 5/6 - 3/10 = 50/60 - 18/60 = 32/60 = 8/15
2) 3/10 + 2/15 = 9/30 + 4/30 = 13/30 
3) 8/15 : 13/30 = 8/15 * 30/13 = 8/1 * 2/13 = 16/13 =  1 3/13