91Ó°ÊÓ

Justify each statement with a property from algebra or a property of congruence.

If $\stackrel{¯}{\mathrm{AB}}â‰\dots \stackrel{¯}{\mathrm{CD}}$and $\stackrel{¯}{\mathrm{CD}}â‰\dots \stackrel{¯}{\mathrm{EF}}$then $\stackrel{¯}{\mathrm{AB}}â‰\dots \stackrel{¯}{\mathrm{EF}}$.

Describe your plan for proving the following. You don’t need to give all the details.

Given:∠3 is supplementary to∠1;∠4 is supplementary to∠2.

Prove: $∠3â‰\dots ∠4$

Give a plan for the following proof.

Given:∠1 is supplementary to∠3;∠2 is supplementary to∠3.

Prove:$\mathbf{j}\mathbf{âŠ\yen }\mathbf{k}$

Write the name or statement of the definition, postulate, or theorem that justifies the statement about the diagram.

If $∠4â‰\dots ∠3$, then$\stackrel{↔}{DG}$ bisects $∠BDE$.

Solve each system of equations by the substitution method.

$x–7y=13$

$3x–5y=23$

Name or state the postulate, property, definition or theorem that justifies the statement.

If W is the midpoint of $\stackrel{¯}{\text{XV}}$, then $\text{XW}=\frac{1}{2}\text{XV}$.

Name the definition or state the theorem that justifies the statement about the diagram.

If $\stackrel{↔}{RS}âŠ\yen \stackrel{↔}{TV}$, then $∠8â‰\dots ∠7$.

1. Name a supplement of $\mathbf{∠}\mathit{M}\mathit{L}\mathit{Q}$.
2. Name another pair of supplementary angles.
   
   

Name the definition or state the theorem that justifies the statement about the diagram.

If $∠ABEâ‰\dots ∠EBC$, then $\stackrel{↔}{AC}âŠ\yen \stackrel{→}{BE}$.

Write each biconditional as two conditionals that are converses of each other.

Points are collinear if and only if they all lie in one line.