Add [tex] \frac{x}{2} [/tex] to both sides:
[tex] \dfrac{2x}{5}+\frac{x}{2} = 9 [/tex]
Add the fractions in the left hand side:
[tex] \dfrac{2x}{5}+\frac{x}{2} = \dfrac{4x}{10}+\frac{5x}{10}=\dfrac{9x}{10} [/tex]
So, the equation becomes
[tex] \dfrac{9x}{10}= 9 [/tex]
Multiply both sides by 10:
[tex] 9x = 90 [/tex]
Divide both sides by 9:
[tex] x = 10 [/tex]
