(y= mx + b). consider M (your fraction) as rise over run. And B (-4) as your starting point. You start at "-4" and rise up 1, run over two to the right. You would go to the left if there was a negative sign on there.
Hello! So, in order to solve this question, we should do 500/4. 500/4 = 125. Multiply 125 by 3 and you get 375. The horse costs $125 and the carriage costs $375.