The number of hours studied by Lennox is 18 hours.
Let the number of hours studied by Danielle be h.
According to the question,
Number of hours Althea studied = (h + 5) hours
Number of hours Lennox studied = 2(h + 5) hours
Hence,
h + (h + 5) + 2(h + 5) = 31
h + h + 5 + 2h + 10 = 31
4h + 15 = 31
4h = 31 - 15 = 16
h = 16/4 = 4 hours
Hence,
The number of hours studied by Lennox = 2 (h + 5) = 2(4+5) = 18 hours.
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