Choice C is the correct answer. When riding toward each other, they close the gap at the sum of their speeds.

Let $t$ = time in hours.

Combined speed: $12 + 18 = 30$ mph

Equation: $30t = 90$$t = 3$

Solution: 3 hours

Verification: In 3 hours:

• Cyclist 1: $12(3) = 36$ miles
• Cyclist 2: $18(3) = 54$ miles
• Total: $36 + 54 = 90$ miles ✓

💡 Strategic Tip: Toward each other → add speeds.

**Other choices based on calculation.