Main Activity: The idioms below have one wrong word! Can you replace the wrong word with the correct one and insert the correct word in the crossword, please?

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Across
  1. 2. Did you know that she's working with my old friend from uni?It's a tiny world.
  2. 4. Once you learn your timetables fractions are a peace of cake.
  3. 7. Me and my sister have the best ideas! Great minds sing alike.
  4. 8. My football team won the tournament last night. I was over planet Mars!
  5. 9. Let the cat out of the rucksack.
  6. 10. You are what you think.
  7. 12. I had been saving for this video game since forever. It paid an arm and a leg.
  8. 13. River under the bridge
Down
  1. 1. I am all wet because it has been throwing cats and dogs.
  2. 2. Are you a light traveller? Yes I have packed everything but the kitchen towel.
  3. 3. Are you serious? No I am pulling your hand.
  4. 5. You must not look through others people's phones. Curiosity killed the magpie.
  5. 6. Cross your toes that there will be no test tomorrow.
  6. 11. I told my teacher I hadn't done my homework and she jumped off the handle.
  7. 12. Well, it is up to you now. The ball is in your pitch.