Question

Help is greatly needed....

Answer 1

slope formula
points (1,40) and (4,85)
m=
`(y_(2)- y_(1) )/(x_(2)-x_(1))`
m=
`(85-40)/(4-1)`
m=
`(45)/(3)`


y=mx+b
y=40; x=1; m= 45/3

40=(45/3) + b
40 - (45/3)= b
b= 25

therefore

y=(45/3)x + 25
when x=0
y=25

so the value of the book was $25