The equation of the linear regression line represents the relationship between the number of cars washed for charity, x, and the amount earned for the charity, y. yˆ=10x+20 What does the slope of the line represent? For every car washed for charity, the amount earned for the charity increases by $10. For every car washed for charity, the amount earned for the charity increases by $20. For every car washed for charity, the amount earned for the charity increases by $1. For every car washed for charity, the amount earned for the charity increases by $2.