Suppose the percent of the total work force that is female is given by
p(t) = −0.0033t2 + 0.46t + 35
where t is the number of years past 1970.
in what year is the percent of women workers at its maximum, according to this model?

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.