Find the Sum of the First Two Polynomials

$\text{Sum} = (2x - 3y + 7z) + (-5x + 4z)$ Combine like terms: $x\text{-terms: } 2x - 5x = -3xy\text{-terms: } -3yz\text{-terms: } 7z + 4z = 11z\text{Sum} = -3x - 3y + 11z$

Sum $= -3x - 3y + 11z$

Subtract Sum from (13x - z)

$(13x - z) - (-3x - 3y + 11z) = 13x - z + 3x + 3y - 11z$ Combine like terms: $(13x + 3x) + 3y + (-z - 11z) = 16x + 3y - 12z$

Result $= 16x + 3y - 12z$