tolong di jawab y, peke cara... semua

1)
a. ΔACD dan ΔBCD
b. [∠ABC=∠CAB=75°] dan [∠ACB=2x15°=30°]

2)
∠CBD = ∠ABC : 2 = 60° : 2 = 30°
∠ABD = ∠CBD = 30°
∠ADB = 180° - ∠BDC = 180° - 60° = 120°
∠BAD = 180° - ∠DCB - ∠ABC = 180° - 90° - 60° = 30°

3)
a. ∠A + ∠B + ∠C = 180°
<=> (2x) + (3x + 20°) + (5x - 40°) = 180°
<=> 10x - 20° = 180°
<=> 10x = 180° + 20°
<=> 10x = 200°
<=> x = 200° : 10
<=> x = 20°
b. [∠A = 2x = 2 x 20° = 40°]
[∠B = 3x + 20° = 3 x 20° + 20° = 60 + 20° = 80°]
[∠C = 5x - 40° = 5 x 20° - 40° = 100° - 40° = 60°]

4)
a. [z = 180° - 150° = 30°]
[3y = 180° - 105° - z = 180° - 105° - 30° <=> 3y = 45° <=> y = 45° : 3 = 15°]
b. ∠PQR = 3y = 3 x 15° = 45°

5)
a. (2x - 1) + (x + 3) + (5x - 1) = 9
<=> 8x + 1 = 9
<=> 8x + 1 (-1) = 9 (-1)
<=> 8x = 8
<=> x = 8 : 8
<=> x = 1
b. [2x - 1 = 2 x 1 - 1 = 2 - 1 = 1]
[x + 3 = 1 x 1 + 3 = 1 + 3 = 4]
[5x - 1 = 5 x 1 - 1 = 5 - 1 = 4]