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 ?	Select the correct option:
A) 4x + 6y
B) x + y + 4
C) 4x - 9y
D) 9x + 4y
E) x + y - 4
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.   correct 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 following will be divisible by 11 ?