Question 1: The square represents 18.

 Question 2: The triangle represents 40.

 Question 3: The rectangle represents 35.

 Question 4: The square represents 192.

You may have found this one a little bit tricky.  We had to use our CI scale again, but because the unknown number was on the denominator we had to use the C scale to place the 64 and not the CI scale.  Can you see why?

In the problem, 64 is not on the denominator, so it doesn't make sense to use the CI scale (inverse scale) since we are dealing with 64 not ¹/₆₄.

 Question 5: The triangle represents 351.