=>9-25=7-x-25-7
=>x=7-25-7-9+25
=>x=(7-7)+(25-25)-9
=>x=0+0-9
=>x=-9
7 - x - 25 - 7 = 25 - 9
x = 7 - 25 -7 + 25 + 9
x = (7-7)+(25-25) + 9
x= 9
tick cho tui đủ 110 nghen
ta có ; 7-x-25-7=25-9
x=7-25-7+25+9
x=(7-7)+(25-25)+9
x=9
9 -25 = (7-x) -(25+7) <=>9- 25 = 7 -x - 25-7 <=> x =7 -25 -7-9+25 <=> x = ( 7-7) + ( 25-25) -9 <=> x = 0+0-9 <=> x = -9