When asked for possible solutions, I find it easier to graph the constraint equations and read values from the feasible region.
a) Possible numbers of (front page, inside) ads include ...
(10, 10), (12, 9), (14, 8), ..., (30, 0)
b) Let x and y represent the numbers of front-page and inside ads, respectively.
2x +y ≤ 30 . . . . . . . the advertising budget is $30
x +y ≥ 20 . . . . . . . . there should be at least 20 ads
c) The solution region is the one doubly-shaded (purple).
