Question 159100
The formula for slope is,
{{{m=(y[2]-y[1])/(x[2]-x[1])}}}
Let's substitute,

{{{-3/4=(6-8)/(a-5)}}}
Cross multiplying,
{{{-3(a-5)=4(-2)}}}
{{{a-5=8/3}}}
{{{a=15/3+8/3}}}
{{{a=23/3}}}