Answer:
[tex]\Large \boxed{a=\frac{-1}{4} }[/tex]
Step-by-step explanation:
[tex]\displaystyle \frac{3}{a} \cdot x - 4 = 20[/tex]
Let x = -2.
[tex]\displaystyle \frac{3}{a} \cdot (-2) - 4 = 20[/tex]
Solving for a.
[tex]\displaystyle \frac{-6}{a}- 4 = 20[/tex]
Adding 4 to both sides.
[tex]\displaystyle \frac{-6}{a} = 24[/tex]
Multiplying both sides by a, then dividing both sides by 24.
[tex]\displaystyle \frac{-6}{24} = a[/tex]
Simplifying.
[tex]\displaystyle \frac{-1}{4} = a[/tex]
