For 10 values denoted by \( x \), it is given that \(\displaystyle \bar{x} = 7.4\). Find \(\displaystyle \Sigma x\).

For 10 values denoted by \( x \), it is given that \(\displaystyle \bar{x} = 7.4\). Find \(\displaystyle \Sigma (x+2)\).

For 10 values denoted by \( x \), it is given that \(\displaystyle \bar{x} = 7.4\). Find \(\displaystyle \Sigma (x-1)\).

Twenty-five values of \( z \) are such that \(\displaystyle \Sigma (z - 7) = 275\). Find \(\displaystyle \bar{z}\).

Given \(\displaystyle \bar{q} = 22\) and \(\displaystyle \Sigma (q - 4) = 3672\), find the number of values of \( q \).

The lengths of 2500 bolts (\( x \) mm) are summarised by \(\displaystyle \Sigma (x - 40) = 875\). Find the mean length of the bolts.