2.1.3. \( -9(-6+6)=(-9 \times \square)+(-9 \times \square)=\square+\square=\square \)

Let's break this down! The expression \( -9(-6+6) \) simplifies to \( -9(0) \), since \(-6 + 6\) equals zero. Multiplying anything by zero results in zero, so \( -9(0) = 0 \). Now, if we take \(-9\) and distribute it through the parentheses, we have: \[ -9 \times -6 + -9 \times 6 = 54 - 54 \]. This again results in \(0\), verifying our earlier conclusion. So overall, the equation simplifies to \(0 = 0 + 0\). Thus, the boxes can be filled with \(0\) since every operation equals zero! Fun fact: zero is quite the hero in math—the identity element for addition!