Answer: [tex]A=15[/tex]
Step-by-step explanation:
You have the following equation:
[tex] 3A + B = 54[/tex]
In order to find the the value of the variable "A" when [tex]B=9[/tex], you need to substitute this value of "B" into the equation and then you must solve for "A".
Applying this procedure, you get:
[tex]3A + B = 54\\\\ 3A + 9 = 54\\\\3A=54-9\\\\3A=45\\\\A=\frac{45}{3}\\\\A=15[/tex]
