7th grade math help??? URGENT!!!!!!!!

Angle sum of a quadrilateral: Angles always add up to 360.
1. Angle A- 5x
B- 10x
C- 17x
D- 4x
x=?

All the angles add up to 360, so

5x + 10x + 17x + 4x = 360

36x = 360

x = 360/36 = 10

you can add all 4 angles together and set them equal to 360 degrees
5x+10x+17x+4x=360
36x=360
x=10