(х-1целая две пятых): 10+7 целых пять двенадцатых=9

(х - 1 2/5) : 10 + 7 5/12 = 9
(х - 1 2/5) : 10 = 9 - 7 5/12 = 8 12/12 - 7 5/12 = 1 7/12
х - 1 2/5 = 1 7/12 * 10 = 19/12 * 10 = 190/12 = 15 10/12 = 15 5/6
х = 15 5/6 + 1 2/5 = 15 25/30 + 1 12/30 = 16 37/30 = 17 7/30
х = 17 7/30