chegg how are the slope and intercept of a simple linear regression line calculated? what do they tell us about the relationship between the two variables?

Maria : 26.50 - 0.25(26.50) = 26.50 - 6.625 = 19.88
            19.87 + 0.10(19.87) = 19.87 + 1.99 = 21.86

Edwin : 0.75(26.50) = 19.88
             1.10(19.88) = 21.86

and if they each have $ 23, then yes, they both ave enough money to buy the book. They both were correct in their calculations. Because taking 25% off, is the same as paying 75%and taking the discount price and subtracting 10% from that, is the same as multiplying by 110%. So they basically worked the same problem, just in a little different way...and they both ended up with the same answer