Question 1048054
{{{f(x)}}={{{-2x-3}}} your equation

{{{f(c-5)}}}={{{(-2(c-5)-3)}}}           plug c-5 everywhere you see x
{{{f(c-5)}}}={{{((-2c+10)-3)}}}            simplify
{{{f(c-5)}}}={{{(-2c+7)}}}