Hey there!
Triangle CBD is congruent to triangle ABD. This means that BD is congruent to BD by reflexive property. You have two congruent angles, and one congruent side. This would be AAS theorem. The answer is D.
I hope this helps!
Answer:
1/3 or .3333333.....
Step-by-step explanation:
Speed of the boat = u
speed of the current = v
In downstream,
u - v = 280/7
u - v = 40
In upstream,
u + v = 280/14
u + v = 20
Add both equations
2u = 60
u = 30
v = -10
Speed of the boat = 30 km/h