Determine x so that the slope of the line through (1, 4) and (x, 2) is 2.

Slope = $\dfrac{y$2 - y1}{x2 - x1}

Substituting values we get,

$\Rightarrow \text{Slope } = \dfrac{2 - 4}{x - 1} \\[1em] \Rightarrow 2 = \dfrac{-2}{x - 1} \\[1em] \Rightarrow 2(x - 1) = -2 \\[1em] \Rightarrow x - 1 = -1 \\[1em] \Rightarrow x = -1 + 1 = 0. \\[1em]$

Hence, x = 0.