On average, Justin takes 1 less hour to assemble a bicycle than Christina. If working together Justin and Christina can assemble 36 bicycles in a combined 80 hours, how long does it take Justin to assemble a bicycle? Do not include the units in your answer.

Look, when you want to do something like put it like x^2. x2 could mean x² or x₂. so to clear confusion, know the notation. to find the product multiply the x's and you get -8x and the y's and you get 6y. since it's all being multiplied it is just -8x6y, or answer a. although the better answer is -48xy(combining -8 and 6) because you should multiply constants whenever you can.