Question

1. $x - 4y - 12 - 5y + 8y - x - 7$\\17. $3x + 7 - 7y + 2x - 3y - 1$\\18. $-9x - y + 1 + 5y + 5x - 10$\\19. $-x + 8 + 6x - 4y - 8x + 3$\\20. $4x - 7 + y - 7x - (-3y)$\\21. $8x - 5y - x + 9 - y$

Explanation:

Let's solve problem 20: \( 4x - 7 + y - 7x - (-3y) \)

Step 1: Simplify the double negative

The term \( -(-3y) \) becomes \( + 3y \), so the expression is \( 4x - 7 + y - 7x + 3y \)

Step 2: Combine like terms for \( x \)

\( 4x - 7x = -3x \)

Step 3: Combine like terms for \( y \)

\( y + 3y = 4y \)

Step 4: Combine the constant term

The constant term is \( -7 \)

Step 5: Write the simplified expression

Putting it all together: \( -3x + 4y - 7 \)

Answer:

\( -3x + 4y - 7 \)