Answer:
[tex]-\frac{17}{2}[/tex]
Step-by-step explanation:
Substitute the point (21,-4) in for [tex]x[/tex] and [tex]y[/tex] in the equation making
[tex]3(21)+B(-4)=97[/tex]
Simplify and solve
[tex]63-4B=97[/tex]
[tex]-4B=34[/tex]
[tex]B=-\frac{17}{2}[/tex]