Y * ( 6 + 11 ) = 321 - 15
Y = 306 : 17
Y = 18
---------------------------
X : 8 = 9 - 7
X : 8 = 2
X = 2 * 8
X = 16
----------------------------
15 * ( 2X + 11 ) = 285
2X + 11 = 285 : 15
2X + 11 = 19
2X = 8
X = 4
---------------------------
56 : X = 8 + 6
56 : X = 14
X = 56 : 14
X = 4