Question

find the number a for which x = 3 is a solution of the giver
x + 3a = 15 + ax - 6a

Explanation:

Step1: Substitute $x=3$ into equation

$3 + 3a = 15 + a(3) - 6a$

Step2: Simplify right-hand side

$3 + 3a = 15 - 3a$

Step3: Isolate terms with $a$

$3a + 3a = 15 - 3$

Step4: Combine like terms

$6a = 12$

Step5: Solve for $a$

$a = \frac{12}{6}$

Answer:

$a=2$