Final answer:
The value of 'a' in the equation 3a + b = 54, when b = 9, is 15. You solve for 'a' by substituting 9 for b, subtracting 9 from both sides, and then dividing by 3.
Step-by-step explanation:
The question asks to find the value of 'a' in the equation 3a + b = 54, given that b equals 9. To solve for a, we substitute the value of b into the equation, thereby getting 3a + 9 = 54. Then, we subtract 9 from both sides of the equation to isolate the term with a, resulting in 3a = 45. Finally, we divide both sides by 3 to find the value of a, which gives us a = 15.