Choice C is the correct answer. Let $A$ = Anna's age and $D$ = daughter's age.

System: $\begin{cases} A = 3D \\ A + D = 48 \end{cases}$

Step 1: Substitute: $3D + D = 48$$4D = 48$$D = 12$

Step 2: Find A: $A = 3(12) = 36$

Solution: Anna is 36 years old

Verification: $36 + 12 = 48$ ✓ and $36 = 3(12)$ ✓

💡 Strategic Tip: "Times as old" translates to multiplication.