The problem provides two ratio equations for positive numbers $X, Y$, and $Z$ :
1.

$$
\(\frac{Z}{Y}=\frac{35}{6}\)
$$

2.

$$
\(\frac{Z}{X}=\frac{35}{8}\)
$$


We need to compare $X$ (Quantity A) and $Y$ (Quantity B).
Since both equations share the same term $Z$ on the left side, we can set up a system of equations for $X$ and $Y$ in terms of $Z$.

From (1), solve for $Y$ :

$$
\(Y=Z \times \frac{6}{35}\)
$$


From (2), solve for $X$ :

$$
\(X=Z \times \frac{8}{35}\)
$$


Now, compare Quantity A and Quantity B:

Since $Z$ is a positive number, we can compare the coefficients (fractions) that multiply $\(Z: \frac{8}{35}$ and $\frac{6}{35}\)$.

Since the denominators are equal, we look at the numerators: $8>6$. Therefore, $\(\frac{8}{35}>\frac{6}{35}\)$.
Since $X$ is a larger positive multiple of $Z$ than $Y$ is, we conclude:

$$
\(X>Y\)
$$


Quantity $A$ is greater than Quantity $B$.
The correct choice is $\(\mathbf{A}\)$.