To find the angle x, you are given the triangle side lengths that are opposite and adjacent to the angle. The opposite side is 49 units long. The adjacent side is 24 units long. The trigonometric function that corresponds to the opposite and adjacent legs is tangent.
to find x: 
to find an angle using a trigonometric function we must use the inverse function.

The angle x, to the nearest tenth of a degree is 63.9 degrees.
Answer: The possible side lengths are either 16 inches or 20 inches
Step-by-step explanation: The aquarium is in the shape of a cube which suggests that, all dimensions (length, width and height) are equal.
If it can hold 4096 cubic inches of water, then the volume of water in it can be calculated as follows;
Volume = L x W x H
Knowing that all three dimensions are the same the formula can be re-written as;
Volume = L³
4096 = L³
Add the cube root sign to both sides of the equation
∛4096 = ∛L³
16 = L
Also if it can hold up to 8000 cubic inches of water, then the volume of water in it can be calculated as;
Volume = L³
8000 = L³
Add the cube root sign to both sides of the equation
∛8000 = ∛L³
20 = L
Therefore, if the aquarium can hold between 4096 and 8000 cubic inches of water, then the side lengths are either 16 inches or 20 inches