x+45-56+375=999
x+45-56=999-375
x+45-56=624
x+45=624+56
x+45=680
x=680-45
x=635
x + 45 - 56 + 375 = 999
x + 45 - 56 = 999 - 375
x + 45 - 56 = 624
x + 45 = 624 + 56
x + 45 = 680
x = 680 - 45
x = 635
Vậy: x có giá trị bằng 635
x + 46 - 56 + 375 = 999
x + 476 - 431 = 999
x = (999 + 431) - 476
x = 950