If x and y are positive integers such that (3x + 7y) is a multiple of 11, then which of the following will be divisible by 11 ?	Choose the correct choice:
A) 9
B) 11
C) 17
D) 21
E) 27
By hit and trial, we put x = 5 and y = 1 so that (3x + 7y) = (3 x 5 + 7 x 1) = 22, which is divisible by 11.   (4x + 6y) = ( 4 x 5 + 6 x 1) = 26, which is not divisible by 11;   (x + y + 4 ) = (5 + 1 + 4)= 
<gadget id="calculator">(5 + 1 + 4)</gadget>
<output>10</output>
10, which is not divisible by 11;   (9x + 4y)= (9 x 5 + 4 x 1) = 49, which is not divisible by 11;   (4x - 9y) = (4 x 5 - 9 x 1) = 11, which is divisible by 11.   Option 11
<result>B</result>
If x and y are positive integers such that (3x + 7y) is a multiple of 11, then which of the following will be divisible by 11 ?