Answer:
C. $25
Step-by-step explanation:
We will find,
The slope of the function using [tex]\frac{y_{2}-y_{1}}{x_{2}-x_{1}}[/tex].
Taking the points (1,40) and (2,55).
Slope = [tex]\frac{55-40}{2-1}[/tex]
i.e. Slope = [tex]\frac{15}{1}[/tex]
i.e. Slope = 15
Substituting the slope and point (1,40) in the equation [tex]y=mx+b[/tex],
We have, [tex]40=15\times 1+b[/tex]
i.e. [tex]b=40-15[/tex]
i.e. b= 25
Thus, the equation of the linear function is [tex]y=15x+25[/tex].
This linear function represents the cost of the comic book since Lucy purchased it, where x= years.
So, the initial value of the comic book is when x= 0.
So, [tex]y=15\times 0+25[/tex] i.e. y= 25
Hence, the cost of the book when Lucy purchased it was $25.
