Answer:
3
Explanation:
Paula places a 3 in the box furthest to the left in the synthetic division set-up. In synthetic division, the numbers in the dividend (3x^4−2x^3+x−16) are arranged in a row with a box to the left of the first term. The number placed in this box is the leading coefficient of the polynomial, which is the coefficient of the term with the highest degree. In this case, the leading coefficient of the polynomial is 3, so Paula places a 3 in the box.