The average (arithmetic mean) of y numbers is x. If 25 is added to the set of numbers, then the average will be x - 5. What is the value of y in terms of x ?  Choose one.
A) x/6 - 6	B) x/6 - 5	C) x/7 - 5	D) x/5 - 7	E) x/5 - 6
(A1 + A2 + .. + Ay)/y = x   (A1 + A2 + .. + Ay + 25)/(y+1) = x - 5   =&gt; (xy + 25)/(y+1) = x - 5   =&gt; xy + 25 = yx -5y + x - 5   =&gt; 30 = x - 5y   =&gt; 5y = x - 30   =&gt; y = x/5 - 6   x/5 - 6
<result>E</result>
The average (arithmetic mean) of y numbers is x. If 25 is added to the set of numbers, then the average will be x - 5. What is the value of y in terms of x ?