Algebra

 2x - 5 <= -x + 12 - 7x + 18

Rearrange  as

10x <= 35

x <= 35  / 10

x <= 7 /  2

Put the terms with $x$ on one side and the numbers on the other:

$2x+x+7x \le 12+18+5$

which simplifies to $10x\le35$ 

So $x= \dfrac{7}{2}$. 

I hope that helped!