The average (arithmetic mean) of four numbers is 7x + 3. If one of the numbers is x, what is the average of the other three numbers? Select the correct option:  A) x + 1  B) 9x + 4  C) 5x + 1  D) 5x + 4  E) 15x + 12
If the average of four numbers is 7x + 3, then the sum of all four numbers if 4 * (7x + 3) = 28x + 12. If one of the numbers is x, then the average of the remaining three numbers would be: (28x + 12 - x)/3 = (27x + 12)/3 = 9x + 4.   Answer is 9x + 4.
<result>B</result>
The average (arithmetic mean) of four numbers is 7x + 3. If one of the numbers is x, what is the average of the other three numbers?