Choice D is the correct answer. Let $s$ = student tickets and $a$ = adult tickets.

System: $\begin{cases} s + a = 250 \\ 5s + 10a = 1750 \end{cases}$

Step 1: From first: $a = 250 - s$

Step 2: Substitute: $5s + 10(250 - s) = 1750$$5s + 2500 - 10s = 1750$$-5s = -750$$s = 150$

Solution: 150 student tickets

Verification: $150 + 100 = 250$ ✓ and $5(150) + 10(100) = 750 + 1000 = 1750$ ✓

💡 Strategic Tip: Ticket revenue = quantity × price.

**Other choices fail verification.