Can anyone me on this apparently the answer is 60 but i just can't understand how

∠K and ∠J are supplementary angles. The sum of supplementary angles is 180°

Find x with the property of supplementary angles.
∠K + ∠J = 180°
60 + x + 120 + x = 180°
180° + 2x = 180°
2x = 0
x = 0

We know x = 0, we find ∠J and ∠K
∠J = x + 120° = 120°
∠K = x + 60° = 60°

The two acutes angles each equal 60 + x
The two obtuse angles each equal x + 120

If you set up an equation to solve, it'd be:
2(60 + x) + 2(x + 120) = 360 (since 360 is the total degrees in a quadrilateral)
120 + 2x + 2x + 240 = 360
4x = 0
x = 0 

Since x equals zero, just plug that back into the equation for the measure of angle m.

Measure of angle m = 60 + x 
m = 60 + 0 = 60 degrees 

Ihave, but this question is gonna probably get deleted.