What is the constant of proportionality in the equation y = 2.5x?

we know that

A relationship between two variables, x, and y, represent a direct variation if it can be expressed in the form or

where

k is the constant of proportionality

In this problem we have

so

the constant of proportionality k is equal to

therefore

the answer is

step-by-step explanation:

all three statements are true

step-by-step explanation:

a shipping fee of 5% is charged online with every item purchased online

first let's just take each option and calculate them based on this, to see if the answers matched

keith buys a 40 dollar book

40 x 0.05 = 2

therefore there will be a two dollar fee on keith's book

40 + 2 =42

the first statement is true

a chair costs $80

80 x 0.05 = 4

80 + 4 = 84

the second statement is true

george buys a 20 dollar calculator

20 x 0.05 = 1

20 + 1 = 21

the third statements are true

all three statements are true