To solve for \( x \), where \( x \) equals the number of $4.00 treats Frank can buy, we start with the inequality given:
\[ 4x + 36.00 \leq 52.00 \]
First, we can subtract $36.00 from both sides of the inequality:
\[ 4x \leq 52.00 - 36.00 \]
This simplifies to:
\[ 4x \leq 16.00 \]
Next, we divide each side of the inequality by 4:
\[ x \leq \frac{16.00}{4} \]
This gives us:
\[ x \leq 4 \]
So, the solution is \( x \leq 4 \).
The correct answer is D. x ≤ 4.