The average (arithmetic mean) of y numbers is x. If 20 is added to the set of numbers, then the average will be x - 5. What is the value of y in terms of x ? Select.
A) x/6 - 6	B) x/6 - 5	C) x/7 - 5	D) x/5 - 5	E) x/5 - 6
(A1 + A2 + .. + Ay)/y = x   (A1 + A2 + .. + Ay + 20)/(y+1) = x - 5   =&gt; (xy + 20)/(y+1) = x - 5   =&gt; xy + 20 = yx -5y + x - 5   =&gt; 25 = x - 5y   =&gt; 5y = x - 25   =&gt; y = x/5 - 5   Answer - x/5 - 5
<result>D</result>
The average (arithmetic mean) of y numbers is x. If 20 is added to the set of numbers, then the average will be x - 5. What is the value of y in terms of x ?