Set 13: Systems of Equations

Choice C is correct. Choice C is the correct answer. Let $M$ = Michael's age now and $C$ = cousin's age now. System: $\begin{cases} M = C + 6 \\ (M - 4) + (C - 4) = 20 \end{cases}$ Step 1: Simplify second: $M + C - 8 = 20M + C = 28$ Step 2: Substitute: (C + 6) + C = 28$2C = 22$C = 11 Step 3: Find M: $M = 11 + 6 = 17$ Four years ago: $(18-4) + (12-4) = 14 + 8 = 22 \neq 20$ Strategic Tip: Age difference stays constant over time.