\[\boxed{\text{6.188.}}\]
\[\textbf{а)}\ 4,?5 = 4,5?\ \ \ \]
\[?\ = 5.\ \]
\[\textbf{б)}\ 2,?6 > 1,9?\ \ \ \ \ \ \ \]
\[? = \ от\ 0\ до\ 9.\ \]
\[\textbf{в)}\ 0,?7 < 0,4?\ \ \ \]
\[?\ = 0;1;2;3.\ \ \]
\[\textbf{г)}\ 0,2?9 < 0,37?\ \ \]
\[? = \ от\ 0\ до\ 9.\ \ \ \ \]