Answer:
40°
Step-by-step explanation:
We have parallel lines.
Angles 1 and 2 are alternate angles.
With parallel lines, alternate angles are congruent.
Therefore
[tex]m\angle1=m\angle2[/tex]
[tex]m\angle1=2x+20,\ m\angle2=3x+10\\\\2x+20=3x+10\qquad\text{subtract 20 from both sides}\\\\2x+20-20=3x+10-20\\\\2x=3x-10\qquad\text{subtract}\ 3x\ \text{from both sides}\\\\2x-3x=3x-3x-10\\\\-x=-10\qquad\text{change the signs}\\\\x=10\\\\m\angle1=2(10)+20=20+20=40[/tex]
