Find X in a Cuboid: Volume 90, Height 5, Depth 3

To find the value of $X$, we begin by using the formula for the volume of a cuboid, which is given by $V = \text{height} \times \text{depth} \times \text{width}$.

In this problem, the volume $V$ is 90 cubic units, the height is 5 units, and the depth is 3 units. We need to find the width $X$. So, we write the equation:

$90 = 5 \times 3 \times X$

Simplify the equation:

$90 = 15 \times X$

To solve for $X$, divide both sides of the equation by 15:

$X = \frac{90}{15}$

Calculating the right-hand side, we find:

$X = 6$

Thus, the width of the cuboid, $X$, is 6 units.

The correct answer to the multiple-choice question is choice 4: 6.