17. (3a2 – 2ab + 3b2) - (-a2 – 5ab + 3b2)
18.
5c – [8c – (6 – 3c)]
19.
10x + [3x – (5x – 4)]
20.
3x 2 – [7x- (4x – x2) + 3]
21.
x2 – [ - 3x+ ( 4 – 7x)]

17. 3ab + 8a

18. -6c + 6

19. 8x + 4

20. x - 3

21. 12x - 4

m∠cdf = 43° , m∠gdf = 114°, m∠gde = 23°, m∠edh = 23° , m∠cdh = 157°

step-by-step explanation:

since, it is given that de bisects the angle gdh ⇒ de divides the angle gdh into two equal angles.

⇒ m∠gde = m∠edh

⇒ 8·x   - 1 = 6·x + 5

⇒ x = 3

so, m∠gde = 8·x - 1 = 23°

and m∠edh = 23°

now, it is given ∠cde is an straight angle so, m∠cde = 180°

⇒ m∠cdf + m∠fdg + m∠gde = 180°

⇒ 43° + m∠fdg + 23° = 180°

⇒ m∠fdg = 114°

again, m∠cde = m∠cdh + m∠edh = 180°

m∠cdh + 23° = 180°

⇒ m∠cdh = 157°

3+x

step-by-step explanation: