(x+2)+(x+4)+(x+6)+(x+8)+x=120
(x+x+x+x+x)+(2+4+6+8)=120
5x+20=120
5x=120-20
5x=100
x=100:5
x=20
Vậy x=20
\(\left(x+2\right)+\left(x+4\right)+\left(x+6\right)+\left(x+8\right)+x=120\)
\(\left(x+x+x+x+x\right)+\left(2+4+6+8\right)=120\)
\(x.5+20=120\)
\(x.5=120-20\)
\(x.5=100\)
\(x=100:5\)
\(x=20\)
[ x + 2 ] + [ x + 4 ] + [ x + 6 ] + [ x + 8 ] + x = 120
[ x + 2 ] + [ x + 4 ] + [ x + 6 ] + [ x + 8 ] + [ x + 10 ] = 120
[ x + ( 2 + 4 + 6 + 8 + 10 ) ] = 120
x + 30 = 120
x = 120 : 30
x = 4.