The function rule t(m)=450-8m represents the amount of water t(m) (in liters) in a holding tank after being drained at a rate of 8l/min for m minutes. how much time has passed if there are 274 l of water in the tank

a. 18 min
b. 20 min
c. 22 min
d. 24 min

if you can explain and work it out

Well they give you the equation and they want you to solve for time given that you know the amount of water in the tank.  They tell you T=274 and that

T=450-8m  so using the value T=274 in the equation to the left gives you:

274=450-8m  subtract 450 from both sides

-176=-8m  divide both sides by -8

22=m

So 22 minutes have passed when there is 274L remaining...