The formula for calculating a z-score is is z = (x-μ)/σ, where x is the raw score, μ is the population mean, and σ is the population standard deviation
6(a+3) = 18 + 6a Open the parenthesis and distribute 6a + 18 = 18 + 6a Subtract both sides by 18 6a = 6a Subtract both sides by 6a 0 = 0 Any value of "a" will satisfy this equation.