x+100+20=55+145+200
x+120=400
x=400-120
x=280
9x9x9
=81x9
=729
9^7<6.7^8
=1+1
=2
10 000 + 90 000
= 100 000
= 15 nhé
\(x+20=50+30\)
\(x+20=80\)
\(x=80-20\)
\(x=60\)