tolong dibantoo yaaa flisss

Bab Trigonometri
Matematika SMA  Kelas X

A + B = 10
A = 10 - B

A/sin A = B / sin B
(10 - B)/sin 30° = B / sin 45°
(10 - B) . 1/2 √2 = B . 1/2
5√2 - 1/2 √2 B = B/2
1/2 b + 1/2 √2 b = 5/2
(b + √2)/2 = 5/2
b + √2 = 5
b = 5 - √2