How I get x for number 7

Answer:
x = 50
Step-by-step explanation:
Angles of a triangle add up to 180°. So the third angle of the triangle on the right is:
180° − 43° − 57° = 80°
Vertical angles are congruent, so the angle on the other side is also 80°. Therefore:
x° + x° + 80° = 180°
2x° = 100°
x = 50