Are you trying write it into slope intercept form ?
One liter is equal to 1000 milliliters. Use the conversion to find your answer. 1000 milliliters / 5mL per tube = 200 tubes
7.81 then 7.14 then 7.081 then 7.002
If you just want to solve for h, as it appears, isolate h by dividing both sides of the equation by 6.25.
That leaves h = 16. (16 hours, presumptively).
