Answer: [tex]a=9[/tex]
Reorder the terms
[tex]9(6 + a) = 135[/tex]
[tex](6 * 9 + a * 9) = 135[/tex]
[tex](54 + 9a) = 135[/tex]
Solving
[tex]54 + 9a = 135[/tex]
Solving for variable 'a'.
Move all terms containing a to the left, all other terms to the right.
Add '-54' to each side of the equation.
[tex]54 + -54 + 9a = 135 + -54[/tex]
Combine like terms: 54 + -54 = 0
[tex]0 + 9a = 135 + -54[/tex]
[tex]9a = 135 + -54[/tex]
Combine like terms: 135 + -54 = 81
[tex]9a = 81[/tex]
Divide each side by '9'
[tex]a=9[/tex]
