Factor the trinomial.
w2 + 15wf +542

From the given scenario in this item, we can say that the sum of x and y is 500. By the aluminum balance, the equation that we can formulate from this,
                            0.25x + 0.40y = (500)(0.35)
The system of linear equations that can best express the given is,
                                   x + y = 500
                                0.25x + 0.40y = 175