For explanation purposes I'll call Point A (14,-6) and Point B (12,8) the given points.
To calculate the distance between both points you have to calculate the distance between each coordinate over the x and y axis.
Then apply the Phytagoras theorem to calculate its length.
I'll sketch the points:
x-axis
[tex]base=d_{AB}=x_A-x_B=14-12=2[/tex]y-axis
[tex]heigth=d_{AB}=y_B-y_A=8-(-6)=8+6=14[/tex]Now according to the Phythagoras theorem, the sum of the squared base and the squared heigth of a triangle is equal to the squared hypotenuse:
[tex]a^2+b^2=c^2[/tex]For this triangle:
[tex]\begin{gathered} 2^2+14^2=c^2 \\ c^2=200 \\ c=\sqrt[]{200}=10\sqrt[]{2}=14.14 \end{gathered}[/tex]The distance between both points is 14.14 units.