The correct answer is: $1.5\text{ years}$
Explanation
To convert months to years, divide the number of months by 12 because there are 12 months in a year. Eighteen months is one and a half years.
Steps:
- Write the conversion: $$18\text{ months} = \frac{18}{12}\text{ years}$$
- Simplify the fraction: $$\frac{18}{12} = \frac{3}{2}$$
- Convert to decimal: $$\frac{3}{2} = 1.5$$
Therefore, $18\text{ months} = 1.5\text{ years}$.