10) These angles are vertical angles.
Whenever two lines intersect, vertical angles are always formed.
Vertical angles are always congruent so we know that b = 43°.
1) Notice that there is a box at the vertex of <EBF.
This tells us that it measures exactly 90 degrees.
Also note that <ABC is a straight angle which means its 180 degrees.
So we have x + 10 + 90 + 2x + x = 180.
First simplify the left to get 4x + 100 = 180.
Solving from here, we find that x = 20.
2) Notice that <AEC and <DEB are vertical angles.
Vertical angles are congruent so we
can setup the equation 3x + 18 = 5x + 6.
First subtract 3x from both sides to get 18 = 2x + 6.
Now subtract 6 from both sides to get 12 = 2x.
Solving from here, we have x = 6.