Answer: Option A.
Explanation:
Simplifying
xy + -9z = 4
Solving
xy + -9z = 4
Solving for variable 'x'.
Move all terms containing x to the left, all other terms to the right.
Add '9z' to each side of the equation.
xy + -9z + 9z = 4 + 9z
Combine like terms: -9z + 9z = 0
xy + 0 = 4 + 9z
xy = 4 + 9z
Divide each side by 'y'.
x = 4y-1 + 9y-1z
Simplifying
x = 4y-1 + 9y-1z