Final answer:
To solve the equation 129 = 7x + 73a for the variable, subtract 73a from both sides and then divide both sides by 7.
Step-by-step explanation:
To solve the equation 129 = 7x + 73a for the variable, we need to isolate x on one side of the equation. First, subtract 73a from both sides to get 129 - 73a = 7x. Then, divide both sides by 7 to solve for x. The final equation is (129 - 73a)/7 = x.