Which of the following is not equal to 63.7 mm?

6.37 x 10 4 µm
6.37 x 10 -5 km
637 cm
0.637 dm

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.

The answer is b. (-13).