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(i) 2a + 3a + 70 = 180
5a = 110
a = 22

2a = 2(22)
=44°
3a = 3(22)
=66°

(ii) b + 57 + 33 = 180
b = 90°

(iii) 45 + 4c + 5c = 180
9c = 135
c = 15

4c = 4(15)
=60°
5c = 5(15)
= 75°

(iv) 7d + 3d + 2d = 180
12d = 180
d = 15

7d = 7(15)
= 105°
3d = 3(15)
= 45°
2d = 2(15)
=30°

(i) 70° + 2a + 3a = 180°
5a = 180°-70°
5a = 110
a = 22

2a = 2×22 = 44°
3a = 3×22 = 66°

(ii) 57+33+b = 180°
b = 180 - (57+33)
= 180-24
= 124°

(iii) 45+4c+5c = 180°
9c = 180-45
9c = 135
c = 15

4c = 4×15 = 60°
5c = 5×15 = 75°

(iv) 3d+7d+2d = 180°
12d = 180°
d = 15

3d = 3×15 = 45°
7d = 7×15 = 105°
2d = 2×15 = 30°