For some given data,if $M + \bar{x} = 165$ and $M - \bar{x} = 1$,then $Z = \dots$

The median of the following frequency distribution is $46$ and the total frequency is $230$. Find the missing frequencies $x$ and $y$.

Class	$10-20$	$20-30$	$30-40$	$40-50$	$50-60$	$60-70$	$70-80$
Frequency	$12$	$30$	$x$	$65$	$y$	$25$	$18$

In the formula $\bar{x} = A + \frac{\Sigma f_{i} u_{i}}{\Sigma f_{i}} \times c$ for the mean,$u_{i} = \ldots \ldots \ldots$

Is it correct to say that an ogive is a graphical representation of a frequency distribution? Give reason.

In the formula $Z = l + \left( \frac{f_{1} - f_{0}}{2f_{1} - f_{0} - f_{2}} \right) \times c$ for the mode,$c = \dots$

The mean of the following data is $26.5$ and the total frequency is $60$. Find the missing frequencies $x$ and $y$.

Class	$0-10$	$10-20$	$20-30$	$30-40$	$40-50$
Frequency	$6$	$x$	$17$	$y$	$8$