=> x - 750 + 100 -550 = 450
=> x-750 + 100=1000
=> x - 750=900
=> x=1650
có x-750+100-550=900:2
=) x-1200=450
x=450+1200
x=1650
x - 750 + 100 - 550 = 900 : 2
x - 750 + 100 - 550 = 450
x - 750 + 100 = 450 + 550
x - 750 + 100 = 1000
x - 750 = 1000 - 100
x - 750 = 900
x = 900 + 750
x = 1650
có x-750+100-550=900:2
=)x-1200=450
x=450+1200
x=1650
x-750+100-550=900/2
x-750+100-550=450
x=450+550-100+750
x=1650