To find the width of the rectangular tabletop given its area and length, we can use the formula for the area of a rectangle:
\[ \text{Area} = \text{Length} \times \text{Width} \]
We know the area is 1,512 square inches and the length is 18 inches. We can set up the equation:
\[ 1,512 = 18 \times \text{Width} \]
To solve for the width, we can divide both sides by 18:
\[ \text{Width} = \frac{1,512}{18} \]
Now we perform the division:
\[ \text{Width} = 84 \text{ inches} \]
Thus, the width of the tabletop is \( \boxed{84} \) inches.