\( \begin{array}{ll}-x+6 x y-y-20 & \text { per } x=-1, y=-3 \\ -3(a+b)+(2 a+3) & \text { per } a=-5, b=+4 \\ -x(-5+a)+2 a x & \text { per } a=-3, x=1 \\ 6 x+3 x y-5(x-y) & \text { per } x=-4, y=-2 \\ -(x-2 x y)-(x-y)-x y & \text { per } x=5, y=-2\end{array} \)

To evaluate each expression at the given values, let's dive into the calculations with a splash of enthusiasm! For the first expression, we plug in \( x = -1 \) and \( y = -3 \): \[ -x + 6xy - y - 20 = -(-1) + 6(-1)(-3) - (-3) - 20 = 1 + 18 + 3 - 20 = 2 \] Now onto the second expression with \( a = -5 \) and \( b = 4 \): \[ -3(a + b) + (2a + 3) = -3(-5 + 4) + (2(-5) + 3) = -3(-1) - 10 + 3 = 3 - 10 + 3 = -4 \] For the third expression with \( a = -3 \) and \( x = 1 \): \[ -x(-5 + a) + 2ax = -1(-5 - 3) + 2(-3)(1) = -1(-8) - 6 = 8 - 6 = 2 \] Next, we evaluate the fourth expression with \( x = -4 \) and \( y = -2 \): \[ 6x + 3xy - 5(x - y) = 6(-4) + 3(-4)(-2) - 5(-4 + 2) = -24 + 24 + 10 = 10 \] Lastly, for the fifth expression with \( x = 5 \) and \( y = -2 \): \[ -(x - 2xy) - (x - y) - xy = -(5 - 2(5)(-2)) - (5 - (-2)) - (5)(-2) = -(5 + 20) - (5 + 2) + 10 = -25 - 7 + 10 = -22 \] To sum it all up, we get: 1. \( 2 \) 2. \( -4 \) 3. \( 2 \) 4. \( 10 \) 5. \( -22 \) And there you have it! Evaluating expressions can be a numerical adventure filled with surprises. 🌟 Happy calculating!