<PRE><B>Question 874978</B>
we know BC = AD since they are both diagonals of the parallelogram(ABCD), therefore
3x + 3y = 21
x + y = 7
now AB = CD since they are congruent sides of ABCD
2x + 4y = 6y + 0.5x
solve first equation for y
y = 7 - x
substitute for y in the second equation
2x + 4(7-x) = 6(7-x) +0.5x
2x + 28-4x = 42-6x +0.5x
-2x+28 = 42 -5.5x
3.5x = 14
x = 4
y = 3
</PRE>