Answer:
[tex]\huge\boxed{\sf x = 8a}[/tex]
Step-by-step explanation:
[tex]\sf \frac{3}{a} x - 4 = 20\\\\Add \ 4 \ to \ both \ sides\\\\\frac{3}{a} x = 20+4\\\\\frac{3}{a} x = 24\\\\Multiply \ both \ sides \ by \ a\\\\3x = 24 * a\\\\Divide \ 3 \ to \ both \ sides\\\\x = 24a / 3\\\\x = 8a\\\\\rule[225]{225}{2}[/tex]
Hope this helped!
~AH1807