Answer:

Explanation:
Given: For every 45 pieces of blue yarn Sofia uses, she uses 18 pieces of red yarn
To find: equation that can be used to represent the proportional relationship between the amount of blue yarn, b, and red yard, r
Solution:
As for every 45 pieces of blue yarn Sofia uses, she uses 18 pieces of red yarn,
number of pieces of blue yarn / number of pieces of red yarn =


Therefore,
equation that can be used to represent the proportional relationship between the amount of blue yarn, b, and red yard, r is
