The mean of two numbers x and y is 4. Find the mean of four numbers x, 2x, y and 2y

The straight line y = mx - 4 passes through the point(-4,16). Calculate the gradient of the line

If the equations x\(^2\) - 5x + 6 = 0 and x + px + 6 = 0 have the same roots, find the value of p.

A trader made a loss of 15% when an article was sold. Find the ratio of the selling price  : cost price

Given that log\(_3\) 27 = 2x + 1, find the value of x.