Answer:
17) x= 36
18)
Explanation:
17) 2x + 2x + x =180°(angles of a triangle)
 5x = 180°
 divide both sides by 5
 X = 36
18) 7x +3x + 90° = 180°(angles of a triangle)
 10x = 90
 X = 9
19) 2x + x + x = 180° (angles of a triangle)
 4x = 180°
 X = 45
hope it helps