Chapter 4 - An Introduction to Functions - 4-5 Writing a Function Rule - Standardized Test Prep - Page 267: 33

B

B is the correct answer because the slope or the rate of the equation is $2.99/lb and x is the independent variable as it represents the number of pounds. The question is asking for the remaining change from a 50 dollar bill after buying x pounds of cherries so the rate is negative as you are taking subtracting the cost of cherries from the 50 dollar bill. Therefore the equation is y= 50-2.99x which matches . C & D are wrong because in both equations, 50 is the slope which is incorrect as 50 is just the initial amount whereas 2.99 is the rate. A is wrong too because even though the rate is 2.99 for this equation, the rate is positive which is incorrect because we are subtracting the cost of the cherries from the initial amount and not the other way as portrayed in A.