x*3x*7=900:100*4
X* (3+7)= 36
X* 10 +36
X= 36:10
X =3,6
x * 3 + x * 7 = 900 : 100 * 4
x * ( 3 + 7 ) = 2,25
x * 10 = 2,25
x = 2,25 : 10
x = 0,225
Vậy x = 0,225
\(\Rightarrow x\cdot\left(3+7\right)=9\cdot4=36\Rightarrow10x=36\Rightarrow x=3.6\)
x*3+x*7=36
x*3+x*7=x*(3+7)=36
x*10=36
x=36 : 10
x= 3.6