X+X:5x7,5+X:2x9=315
X+Xx1,5+Xx9/2=315
Xx(1+1,5+9/2)=315
X x 7=315
=> X=45
\(x+\frac{x}{5}\times7,5+\frac{x}{2}\times9=315\)
\(\Leftrightarrow x+\frac{3}{2}\times x+\frac{9}{2}\times x=315\)
\(\Leftrightarrow7\times x=315\)
\(\Leftrightarrow x=315\div7\)
\(\Leftrightarrow x=45\)
không viết lại đề nha
\(x+\frac{x}{5}\times7,5+\frac{x}{2}\times9=315\)
\(\frac{10\times x}{10}+\frac{2\times x\times7,5}{10}+\frac{5\times x\times9}{10}=\frac{3150}{10}\)
\(10\times x+2\times7,5\times x+5\times9\times x=3150\)
\(10\times x+15\times x+45\times x=3150\)
\(\left(10+15+45\right)\times x=3150\)
\(70\times x=3150\)
\(x=3150:70\)
\(x=45\)
