the salt concentration is (C), (t)is minutes is given by
c(t)= 10t/25+t
where c is measured as grams per liters. when does the salt concentration reach 3.75g/l ?
I'll assume that this is 10t / { 25 + t ]
So
3.75 = 10t / [ 25 + t] multiply both sides by 25 + t
3.75 [ 25 + t] = 10t simplify
93.75 + 3.75 t =10 t subtract 3.75 t from both sides
93.75 = 6.25 t divide both sides by 6.25
t =15 (min)
