#18. C. 1&3
This is be cause when you simplify to y=.. for 4y=3x and 8y=6x, they both turn out to be y=3/4x. The constant of proportionality is 3/4 because both equations simplify to have that as a constant.
#19. D
Kathy can add less than or equal to 7 books to her suitcase.
To cross off the first two choices(A&B), you input a number above 7 and then multiply it by 1 3/4 . Add it to 37 1/2 and it will be more than 50, meaning it will not fit since the suitcase can’t have more than 50 pounds in it.
To cross off C, you would multiply 1 3/4 by 7 and get 12.25. Add 12.25 to 37 1/2 and you will get 49.75 . This result would mean that you can have less than 7 books or just 7 books, leaving the answer to be D.