Answer:
[tex]\huge\boxed{\sf 7.5 \ hours}[/tex]
Step-by-step explanation:
Given that,
36 caterpillars = 15 hours
Using unitary method.
1 caterpillar = 15/36 hours
1 caterpillar = 0.416 hours
1 × 18 caterpillars = 0.416 × 18 hours
[tex]\rule[225]{225}{2}[/tex]