(40 + 54 + x) : 9 + 312 = 323 => (94 + x) : 9 = 323-312 =>
94 + x
---------- = 11 => 94 + x = 99 => x = 99-94 => x = 5
9
4 x [(4 * x - 72) : 4 + 20] = 20+64 => [(4*x-72) : 4 + 20] = 84 : 4
4*(x-18)
(4*x-72) : 4 = 21-20 => ------------ = 1 => x-18=0 => x=18
4