We are given the expression 3x² - y³- y³ - z. We collect like terms to simplify it to something with fewer terms.
3x² - y³- y³ - z
= 3x² - 2y³- z
Now we evaluate for X= 3, Y= -2, and Z= -5
= 3(3²) -2(-2³) - (-5) <--- by putting x and y and z as given
= 3(9) -2(-8) - (-5) <----- by order of operations or PEMDAS
= 27 - (-16) - (-5) <------- multipication comes next
= 27 - (-16) + 5 <---- there's a negative outside, and it comes with an "invisible 1" that gets multiplied throughout, making it + (-1)(-5)
= 27 + 16 + 5 <----same as with the last term
= 27 + 21
= 48
Thus, the expression evaluates to 48.