(490 - x) - 250 = 70
490 - x - 250 = 70
x = 240 - 70
x = 170
(1604 - x) - 108 = 800
1604 - x - 108 = 800
x = 1496 - 800
x = 696
(456 + 112) - x = 400
568 - x = 400
x = 568 - 400
x = 168
(x + 54) - 28 = 38
x + 54 - 28 = 38
x = 38 - 26
x = 12
999 - x = 223 * 4
x = 999 - 892
x = 107
x : 7 = 323 - 299
x = 24 * 7
x = 168
x - 145 = 28 * 9
x = 252 + 145
x = 397
2 * (300 + x) = 600
300 + x = 300
x = 300 - 300
x = 0
800 : x - 300 = 500
800 : x = 500 + 300
800 : x = 800
x = 800 : 800
x = 1
(x + 200) : 400 = 2
x + 200 = 2 * 400
x = 800 - 200
x = 600