2010000504

Level: 
Project ID: 
2010000504
Source Problem: 
Accepted: 
0
Clonable: 
1
Easy: 
0
Solve the inequality with the natural variable $x$: $$\sum\limits_{n=1}^x \left(5-\frac12n\right) \geq x $$
$ x\leq 15;\ x\in\mathbb{N}$
$ x\geq 15;\ x\in\mathbb{N}$
$ x\leq 17;\ x\in\mathbb{N}$
$x\in(-\infty;15]$
there is no solution in $\mathbb{N}$