MC: `15(x+2)`
`1/(5x+10)=1/(5(x+2))=(3)/(15(x+2))`
`x/(3x^2+6x)=x/(3x(x+2))=1/(3(x+2))=5/(15(x+2))`
\(\dfrac{1}{5x+10}=\dfrac{1}{5\left(x+2\right)}=\dfrac{3}{15\left(x+2\right)}\)
\(\dfrac{x}{3x^2+6x}=\dfrac{x}{3x\left(x+2\right)}=\dfrac{5}{15\left(x+2\right)}\)