10. 新定义:对非负数$x$“四舍五入”到个位的值记为$＜x＞$,即当$n$为非负整数时,若$n-\frac{1}{2}≤x＜n+\frac{1}{2}$,则$＜x＞=n$;反之,当$n$为非负整数时,若$＜x＞=n$,则$n-\frac{1}{2}≤x＜n+\frac{1}{2}$.例如,$＜0＞=＜0.48＞=0,＜0.64＞=＜1.499＞=1,＜2＞=2,＜3.5＞=＜4.12＞=4$,……试解决下列问题.
(1)填空:①$＜π＞=$;②若$＜2x−1＞=3$,则实数$x$的取值范围为.
(2)求满足$＜x＞=\frac{4}{3}x$的所有非负数$x$的值.
(3)若关于$x$的不等式组$\begin{cases}\frac{2x-4}{3}≤x-1,\\＜a＞-x＞0\end{cases}$的整数解恰有3个,求$a$的取值范围.

(1)①3 ②$1.75 ≤ x＜2.25$
(2)$\because x ≥ 0$,$\frac{4}{3}x$为整数,设$\frac{4}{3}x=k$,$k$为整数,
则$x=\frac{3}{4}k$,$\therefore ＜\frac{3}{4}k＞=k$,
$\therefore k-\frac{1}{2} ≤ \frac{3}{4}k＜k+\frac{1}{2}$,且$k ≥ 0$,
$\therefore 0 ≤ k ≤ 2$,$\therefore k=0,1,2$,则$x=0$,$\frac{3}{4}$,$\frac{3}{2}$.
(3)解不等式组得$-1 ≤ x＜＜a＞$,
由不等式组的整数解恰有3个,得$1＜＜a＞ ≤ 2$,
$\therefore ＜a＞=2$,$\therefore 1.5 ≤ a＜2.5$.