The formula for an average of three numbers is (x+y+z)/3. So if V equals the average, then we find the formula V = (x+y+z)/3 We are now looking for x. We can divide each of the variables in the parentheses by 3, making the formula V = x/3 + y/3 + z/3 So now bring the unwanted variables to the same side as V. V - y/3 - z/3 = x/3 Now multiply both sides by 3 to find x. 3V - y - z = x
