Question 1044359
A bathtub can be filled in 8 min.
 It takes 12 minutes for the bathtub to drain.if the faucet is turned on but the drain is also open, how long will it take to fill the tub?
:
let t = time in min for this to happen
let a full tub = 1
fill is +; drain is -
{{{t/8}}} - {{{t/12}}} = 1
multiply eq by least common multiple of 8 & 12. That's 24. 
Cancel the denominators and you have
3t - 2t = 24
t = 24 min to fill the tub in these conditions