For $10$ values denoted $x,$ it is given that $\overline{x}=7.4.$ Find:

$\Sigma \left(x-1\right)$

Six data values are coded by subtracting $13$ from each. Five of the coded values are $9.3, 5.4, 3.9, 7.6$ and $2.2,$ and the mean of the six data values is $17.6.$

Find the sixth coded value.

The SD card slots on digital cameras are designed to accommodate a card of up to $24 \mathrm{mm}$ in width. Due to low sales figures, a manufacturer suspects that the machine used to cut the cards needs to be recalibrated. The widths, $w \mathrm{mm},$ of $400$ of these cards were measured and are coded in the following table, where $x=w-24.$

Suggest a reason why the widths have been coded in this way.

The SD card slots on digital cameras are designed to accommodate a card of up to $24 \mathrm{mm}$ in width. Due to low sales figures, a manufacturer suspects that the machine used to cut the cards needs to be recalibrated. The widths, $w \mathrm{mm},$ of $400$ of these cards were measured and are coded in the following table, where $x=w-24.$

What percentage of the SD cards are too wide to fit into the slots?

The SD card slots on digital cameras are designed to accommodate a card of up to $24 \mathrm{mm}$ in width. Due to low sales figures, a manufacturer suspects that the machine used to cut the cards needs to be recalibrated. The widths, $w \mathrm{mm},$ of $400$ of these cards were measured and are coded in the following table, where $x=w-24.$

Use the coded data to estimate the mean width of these $400$ cards.

Sixteen bank accounts have been accidentally under-credited by the following amounts, denoted by $\$x.$

$\begin{array}{llllllll}917.95& 917.98& 918.03& 917.97& 918.01& 917.94& 918.05& 918.07\\ 918.02& 917.93& 918.01& 917.88& 918.10& 917.85& 918.11& 917.94\end{array}$

To calculate $\overline{x}$ manually, Fidel and Ramon code these figures using $\left(x-917\right)$ and $\left(x-920\right),$ respectively.

Who has the simpler maths to do? Explain your answer.