Give a backward-chaining proof of the sentence 7 ≤ 3 + 9. (be sure, of course, to use only the axioms given here, not anything else you may know about arithmetic.) show only the steps that leads to success, not the irrelevant steps.

b. give a forward-chaining proof of the sentence 7 ≤ 3 + 9. again, show only the steps that lead to success.