Question 987170
If the graph is vertical then another point on the graph would be (4,1).
Plug that into the updated equation.
{{{7(4)+3(1)=5(4)-b(1)+8}}}
{{{28+3=28-b}}}
{{{b=-3}}}
it'll work with any point so (4,1) was just arbitrary. 
It could have also been (4,1000).