Hi there!
To simplify 2x² - 5y + 3x + 8y - 15x , you would have to add like terms, like adding x's together and y's together.
add 3x and -15x.
3x + (-15x)
3x - 15x
-12x
add -5y and 8y
-5y + 8y
3y
So your final answer is
2x² - 12x + 3y.
Hope this helped!! :>