"Kosuke wrote a mathematics contest consisting of 25 multiple-choice questions. The scoring.system gave 6 points for a correct answer, 2 points for not answering a question, and 1 poont for an incorrect answer. Kosuke for x correct answers and left y questions unanswered. Write an expression, in simplified form for Kosuke's score".
Here's my attempt:
Let f(x,y) be the score Kosuke receives on the test with x correct answers and y questions unanswered. Correct answers, wrong answers, and unanswered questions matter to the score , right? I have the function for answers and unanswered questions but what about incorrect questions? Can I call it z?
So, using f(x,y,z) with x = # correct, y = # unanswered, z = # incorrect, I can get f(x,y,z)=6x+2y+z
since I have 6 points per correct, 2 points per incorrect, and 1 point for every unanswered question. What I'm stuck on is how to find z in terms for x and y. Is z= 25-6x-2y?