If x and y are integers and x=50y + 39, which of the following must be odd?	Answers:
A) xy	B) x + y	C) 3X-1	D) X+2Y	E) 3x+1
x = 50y + 69, since y is integer, 50y will always be even hence 50y + 69 will be odd hence x = odd   you don't know whether Y is even or odd, so you need to try.   A: odd * even = even ; odd*odd= odd -&gt;not true   B: odd + odd = even ; odd+even = odd -&gt; not true   D: odd + 2*odd = odd ; odd + 2*even = odd -&gt; TRUE, stop here.   C: EVEN ...E - EVEN   Answer X+2Y
<result>D</result>
If x and y are integers and x=50y + 39, which of the following must be odd?