Each game pays coins for right answers, and more for a perfect game. It also pays XP, which raises your Level.
Two hints
50/50 removes two wrong answers in a quiz, for 20 coins. Reveal a letter places one letter in Scrambled letters, for 15 coins. Without enough coins, the app says Not enough coins.
More coins
The daily challenge, streak milestones and Achievements pay coins. At the end of a game, Double my coins (ad) doubles them with an optional video; the + on the home screen gives 100 coins the same way.
Review
Words you missed come back in Review, as cards to flip: I knew it, or Again.