Brainliest to correct answer

Answer:
Step-by-step explanation:
Janet ⇒ 3 postcards ⇒ $1.05
Rosi ⇒ 5 postcards ⇒ $1.75
Tanya ⇒ 8 postcards ⇒ $2.80
We see in all 3 cases cost of postcard is same, the cost and numbers are proportional and the relationship is: