Answer: 
Step-by-step explanation:
<h3>
"Sara plotted the locations of the trees in a park on a coordinate grid. She plotted an oak tree, which was in the middle of the park, at the origin. She plotted a maple tree, which was 10 yards away from the oak tree, at the point (10,0) . Then she plotted a pine tree at the point (-2.4, 5) and an apple tree at the point (7.8, 5) What is the distance, in yards, between the pine tree and the apple tree in the</h3><h3>
park?"</h3>
For this exercise you need to use the following formula, which can be used for calculate the distance between two points:

In this case, you need to find distance, in yards, between the pine tree and the apple tree in the park.
You know that pine tree is located at the point (-2.4, 5) and the apple tree is located at the point (7.8, 5).
So, you can say that:

Knowing these values, you can substitute them into the formula and then evaluate, in order to find the distance, in yards, between the pine tree and the apple tree in the park.
This is:

Answer:
Internal validity
Step-by-step explanation:
The internal validity here is weak
Internal validity describes the extent to which an evidence weighs the cause and effect claim. In this study, the internal validity that brought about failure in the new exam is mainly due to the environment where the exam was written and not the new exam itself.
So this validity is weak in claiming that the new exam is not a good substitute for the old exam.
Putting them in the same good environment might help the researchers to draw a better conclusion.