There are quite some typos in the test 11 solutions.
Question 2: The equation doesn't hold.
Question 3: 5/5 should be 5/4.
Question 8: The equation doesn't hold.
Question 14: Case 2: 3C1 + 3C1 + 3C1 is not equal to 3.
Question 23: Some of the factorizations are not correct.
question 26: 2 is skipped in most branches for the case 6.
Question 30: It should be 55/11=5, not 55-11 =5.