Answer
$Q_{total}=20.263kW$
Work Step by Step
Since the weight-lifting machines have no motors they do not produces heat.
The heat dissipated by the treadmills is:
$Q_{motors}=\frac{7*(2.5hp*\frac{745.7W}{1hp})*0.7}{0.77}=11.863kW$
The heat dissipated by the people is:
$Q_{people}=(12+2)*600W=8.4kW$
Then the total heat gain of the room is:
$Q_{total}=$Q_{motors}+$Q_{people}=11.863kW+8.4kW=20.263kW$
