This would be true. On Jupiter you would weigh 234 pounds if you were 100 pounds on Earth.
Explanation:
average speed = total distance travelled / total time travelled
time to travel the first 6km: 6 / 50 = 3/25 (h)
time to travel the next 6km: 6 / 90 = 1/15 (h)
[I think there's problem in the question 'cause 900km/h sounds impossible for normal person to travel in normal condition]
The total time: 3/25 + 1/15 = 14/75 (h)
Average speed over the 12 km drive will be:

You should trust the primary source more.
This is because the primary source is make its conclusion from direct observation, while the secondary source is possibly making reference to another secondary source or to another primary.
The primary source should be trusted more because it is from direct observation.
Answer:
The height of the tree is three (3) deep
Explanation:
It's 3 deep
Under 129, comes 125 and 685;
Under 125, comes 52 : Under 685, comes 511;
Under 52, comes 46 : Under 511, is 601.
This is illustrated below.
129
∧
125,685
|,|
52,511
|,|
46,601