To find the length of the base of the triangle, we can use the formula for the area of a triangle:
\[ \text{Area} = \frac{1}{2} \times \text{base} \times \text{height} \]
We know the area is \(7.5\) square feet and the height is \(2.5\) feet. Let's denote the base as \(b\).
Substituting the known values into the formula, we have:
\[ 7.5 = \frac{1}{2} \times b \times 2.5 \]
To solve for \(b\), first, multiply both sides by \(2\) to eliminate the fraction:
\[ 15 = b \times 2.5 \]
Next, divide both sides by \(2.5\):
\[ b = \frac{15}{2.5} \]
Calculating the right side:
\[ b = 6 \]
Therefore, the length of the base of Ja'Miles's sign is \(6\) feet.
The correct response is 6 feet.