step 1
Find the equation of the proportional line
C=kW
where k is the constant of proportionality
we have the point (7,17.5)
k=C/W
k=17.5/7
k=2.5
so
the equation is
C=2.5W
Verify the statements
A) 2.5 pounds of peanuts costs $1
For W=2.5
Find the value of C
C=2.5(2.5)=$6.25
the statement is false
B) 1 pound of peanuts costs $2.50
For W=1
C=2.5(1)=$2.5
the statement is true
C) 5 pounds of peanuts cost $12.50
For W=5
C=2.5(5)=$12.5
the statement is true
D) 9 pounds of peanuts cost $19.50
For W=9
C=2.5(9)=$22.5
the statement is false