1. The problem asks us to find an expression equivalent to $7d + 9d - d$. 2. We use the rule of combining like terms: terms with the same variable can be added or subtracted by adding or subtracting their coefficients. 3. Combine the coefficients of $d$: $$7d + 9d - d = (7 + 9 - 1)d$$ 4. Simplify inside the parentheses: $$7 + 9 - 1 = 15$$ 5. So, the expression simplifies to $$15d$$ 6. Therefore, the equivalent expression is $15d$.