Evaluate the following expressions given the values below.  

1. $ab+bc+ac$ for $a=2$, $b=5$, and $c=3$

   Hint (a):

   Substitute the values given for $a$, $b$, and $c$ into the equation.

   $(2)(5)+(5)(3)+(2)(3)$

   Answer (a):

   $=31$

2. $\frac { 20 - x ^ { 2 } } { y - x }$ for $x=−2$ and $y=6$ 

   Hint (b):

   See the hint in part (a).