when a person aged 39 is added to a group of n people, the average age increases by 2. when a person aged 15 is added instead, the average age decreases by 1. what is the value of t?  Pick one:
A) 7  B) 8  C) 9  D) 10  E) 11
<gadget id="calculator">39 - 15</gadget>
<output>24</output>

<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<gadget id="calculator">24 / 3</gadget>
<output>8</output>

<gadget id="calculator">8 - 1</gadget>
<output>7</output>

<result>A</result>
when a person aged 39 is added to a group of n people, the average age increases by 2. when a person aged 15 is added instead, the average age decreases by 1. what is the value of t?
subtract(divide(subtract(39, 15), add(2, 1)), 1)
"a simple and elegant solution . as addition of 39 , shifts mean by 2 , and addition of 15 , shifts mean by 1 to the other side , we have the mean lying between 3915 , and in a ratio of 2 : 1 39 - 15 = 24 24 divide by 3 is 8 . meaning mean of the n terms is 15 + 8 = 39 - 16 = 23 now , from first statement , when a person aged 39 is added to a group of n people , the average age increases by 2 . t * 23 + 39 = 25 * ( t + 1 ) t = 7 ans . ( a )"