1. **Problem statement:** Factor the expression $zac - bc$ using grouping. 2. **Formula and rules:** Grouping involves factoring common terms from parts of the expression. 3. **Step-by-step solution:** - Original expression: $zac - bc$ - Factor out the common term $bc$ from both terms: $$zac - bc = bc\left(\frac{zac}{bc} - 1\right)$$ - Simplify inside the parentheses: $$bc\left(\cancel{b}ac/\cancel{b}c - 1\right) = bc( a z - 1 )$$ 4. **Final factored form:** $$bc(az - 1)$$ This is the fully factored form using grouping.