Question 7086
Solve: {{{c^2 + c - 20}}} ?

This is an expression and you can't solve expressions but you could solve this if it were an equation such as:
{{{c^2 + c - 20 = 0}}}

Let's assume that this is what you meant to write.

{{{c^2 + c - 20 = 0}}} Solve by factoring.
{{{(c + 5)(c - 4) = 0}}} Apply the zero product principle by setting (c+5) = 0 and (c-4) = 0.
If {{{(c + 5) = 0}}}, then {{{c = -5}}}
If {{{(c - 4) = 0}}}, then {{{c = 4}}}

The roots of this quadratic equation are:  x = -5 or x = 4