Notebooks are sold in packages of four or seven only. If Wilson bought 69 notebooks exactly, what could be the number of large packs Wilson bought?  Choose the correct choice from the following choices:
A) 3  B) 4  C) 7  D) 8  E) 9
Let number of packs of four = f   let number of packs of seven = s   4f + 7s = 69   Now , we need to test for values of s .   Since sum 69 is odd and 4f will always be even , e can't be even .   Now , we can test for values e = 3 , 7 and 9   4*5 + 7*7 = 20 + 49= 
<gadget id="calculator">20 + 49</gadget>
<output>69</output>
69   Answer 7
<result>C</result>
Notebooks are sold in packages of four or seven only. If Wilson bought 69 notebooks exactly, what could be the number of large packs Wilson bought?