Respuesta :

Answer:

9

Step-by-step explanation:

All triangles (3 sided polygons) have angles added up to 180, so we can do the following:

(7x-1) + (7x+8) + (5x+2) = 180° - equation

7x-1 + 7x+8 + 5x+2 = 180° - "distribute"

19x - 1 + 8 + 2 = 180° - combine the x terms

19x + 9 = 180° - combine the integer terms

19x = 171 - subtract 9 form both sides

x = 9 - divide both sides by 19