-7 - 12 = - 7х + 3(-4 - x)

x = -1.8

Step-by-step explanation:

-7 - 12 = -7x + 3 (-4 - x)

-7x + 3 (-4 - x) = -7 - 12

P.S I switched the order cuz I find it easier to solve this way.

-7x + 3 (-4 - x) = -7 - 12

Distribute

-7x - 12 - 3x = - 7 + 13

Add 12 to both sides

-7x - 3x = -7 + 13 + 12

Combine like terms

-10x = 18

Divide both sides by -10

x = -1.8

answer:   the paragraph proof is mentioned below.

step-by-step explanation:

given: in a δxwy where

such that, ∠wzx ≅ ∠yzx and zw≅zy

we have to prove that: segment zx is a perpendicular bisector of segment wy.

prove: since, zw≅zy ⇒ ∠wzy is a supplementary angle.

then, ∠wzy= 180°

⇒∠wzx + ∠yzx = 180° ( because xz divides ∠wzy into two parts)

but, ∠wzx ≅ ∠yzx ( given)

⇒∠wzy+∠wzy=180° ( by substitution)

⇒2∠wzy=180°

⇒∠wzy=90°

⇒∠wzy=∠yzx =90°

therefore, xz⊥wy where wz=zy

⇒zx is a perpendicular bisector of wy.