With something like this you have to start out with 3 givens. what I do for these specific kinds of questions is just put something random in the first half, then put something random twice in the second slot, click clear, then it'l give you a button that says "clear" then a little after it'll say "hint" or "demo" the click those buttons and just put the second half in something random until it pops off, this works every time and will allow you to go to the next task.
