Answer:
7. x = 5
8. x = 2, y = 6
9. x = 21, y = 39
Explanation:
For a parallelogram, the lengths across intersection are equal.
7. For a parallelogram, the lengths across intersection are equal.
So that,
3x = 4x - 5
4x - 3x = 5
x = 5
8. For a parallelogram, the lengths across intersection are equal.
So that,
2x = 4
x =

x = 2
and
y - 1 = 2y -7
7 - 1 = 2y - y
y = 6
x = 2, y = 6
9. For a parallelogram, opposite angles have equal value.
Thus,
3x = (4x - 21)
3x = 4x - 21
x = 21
and
3y = (y + 78)
3y = y + 78
3y - y = 78
2y = 78
y =

= 39
y = 39
x = 21, y = 39