Virginia, Adrienne, and Dennis have taught history for a combined total of 93 years. If Virginia has taught for 9 more years than Adrienne and for 9 fewer years than Dennis, for how many years has Dennis taught?  Choose one
A) 23 B) 32 C) 40 D) 41 E) 44
Let number of years taught by Virginia = V   number of years taught by Adrienne = A   number of years taught by Dennis = D   V+A+D = 96   V= A+9   =&gt;A = V-9   V= D-9   =&gt; A = (D-9)-9 = D-18   D-9 + D-18 + D = 93   =&gt; 3D = 93 + 27= 
<gadget id="calculator">93 + 27</gadget>
<output>120</output>
120=&gt; D = 40   Answer 40
<result>C</result>
Virginia, Adrienne, and Dennis have taught history for a combined total of 93 years. If Virginia has taught for 9 more years than Adrienne and for 9 fewer years than Dennis, for how many years has Dennis taught?