\(x\cdot1+x\cdot2+x\cdot3=900-420\)
\(x\cdot(1+2+3)=480\)
\(x\cdot6=480\rightarrow x=80\)
X x 1 + X x 2 + X x 3 = 900 - 420
X x ( 1 + 2 + 3 ) = 480
X x 6 = 480
X = 480 : 6
X = 80
X x 1 + X x 2 + X x 3 = 900 - 420
X x ( 1 + 2 + 3 ) = 480
X x 6 = 480
X = 480 : 6
X = 80
vậy X = 80
X x 1 + X x 2 + X x 3 = 900 - 420
X x ( 1 + 2 + 3 ) = 480
X x 6 = 480
X = 480 : 6
X = 80