Correct Answer: 6 hours a day
Explanation:
More Men, Less Hours {Indirect Proportion}
Less Days, More Hours {Indirect Proportion}
m e n 15 : 10 d a y s 12 : 18 ⋮ ⋮ 6 : x
=> 15 * 12 * x = 10 * 18 * 6
=>x = 6
