Each question shows two ratios with one value missing: 3 : 2 = 66 : ___. Working out what the first was multiplied by gives the factor to apply to the second.
The scale factor is always a whole number and never larger than twelve. A factor of thirty-three turns the question into long multiplication, which is a different skill from seeing that two ratios are the same relationship written twice.
Compare the two numbers you have. In 3 : 2 = 66 : ___, the first has been multiplied by 22, so the second is 2 × 22, which is 44.
No, as long as you scale both by the same amount. That is what equivalent means - the relationship between the two numbers has not changed, only their size.
It is the same mathematics in different notation. 3 : 2 = 66 : 44 and 3/2 = 66/44 say exactly the same thing. Our proportion questions use the fraction form, and the mixed sheets put both on one page on purpose.
Sixth grade, usually right after ratios are introduced and just before proportions.