Determine the unknown angle measures for the quadrilateral in the diagram.
4xº
3x
2xº

x°= 36°.
Theory. The sum of all internal angles of any quadrilateral equals 360°.
Let's solve.
Knowing that all angles must equal 360°, we can add all the expressions and equal them to 360°:
4x°+3x°+2x°+x°=360°.
4x+3x+2x+x=360
10x=360
x=360/10
x= 36.
x°= 36°.
If this solution is correct, than the equation "4x+3x+2x+x=360" must be true when substituting x by 36. Let's test:
4(36)+3(36)+2(36)+(36)=360 ---> True. Hence, the result is correct.