Help. ​

Since both of the opposite sides are parallel, angle 2 is the exact same as angle 1.

 

mL2 = 160º

 

The two unnamed angles are also equal to each other for the same reason.

The horizontal line bisects the two unnamed angles.

There are 180º in every triangle.

So

 mL2 + 2(mL3) = 180º

160º + 2(mL3) = 180º

2(mL3) = 20º

 

mL3 = 10º