If x and y are positive integers such that (3x+7y) is a multiple of 11, then which of the followings are divisible by 11?
Choose the correct choice from the following.
A) 9x+4y
B) x+y+4
C) 4x-9y
D) 4x+6y
E) 5x+3y
By hit and trial method, we get   x=5 and y=1 such that   3x+7y=15+7= 
<gadget id="calculator">15+7</gadget>
<output>22</output>
22 is a multiple of 11.   (4x+6y)=(4×5+6×1)=26   =&gt; not divisible by 11   (x+y+4)=(5+1+4)= 
<gadget id="calculator">(5+1+4)</gadget>
<output>10</output>
10=&gt; not divisible by 11   (9x+4y)=(9×5+4×1)=49   =&gt; not divisible by 11   (4x−9y)=(4×5−9×1)=20−9=11   =&gt; divisible by 11   Answer : 4x-9y
<result>C</result>
If x and y are positive integers such that (3x+7y) is a multiple of 11, then which of the followings are divisible by 11?