7. x =3 because the other side is 3
and y = 5 because the other side is 10 and 2y when y is 5 is 2*5 which is 10.
8. remember the rules of a parallelogram,the opposite angles and sides are equal, if not, it wont be a parallelogram , so if CD is 6, then AB is also 6, bear in mind that AD is not 6 and BC is not 6 but AD is the same as BC.
9. the total angles in any 4 side shape is 360 degrees, so add the angles which is 137+137+a(we dont know) +b(we dont know) MUST EQUAL 360
remember that a is the same as b so we have
274 + a +a=360
so that is the size of the angle
hope that helps