Answer:
a = 15 when b = 9
Step-by-step explanation:
3 a plus b equals 54 in symbolic terms is 3a + b = 54.
Now, if b = 9, 3a + b = 54 becomes 3a + 9 = 54.
Subtracting 9 from both sides yields an equation for 3a:
3a = 45
Dividing both sides by 3 yields a = 15 when b = 9
