Lesson 9: Dealing with Negative Numbers

Dealing with Negative Numbers

Solve Two More Equations

5 min

Problem

Solve each equation. Show your work, or explain your reasoning.

$\text-3x-5=16$
$\text-4(y-2)=12$

Answer

$x=\text-7$ . Sample reasoning: After adding 5 to both sides, we get $\text{-}3x=21$ . After dividing both sides by -3, we get $x=\text{-}7$ .
$y=\text-1$ . Sample reasoning: After dividing both sides by -4, we get $y-2=\text{-}3$ . After adding 2 to both sides, we get $y=\text{-}1$ .

Sample Response

$x=\text-7$ . Sample reasoning: After adding 5 to both sides, we get $\text{-}3x=21$ . After dividing both sides by -3, we get $x=\text{-}7$ .
$y=\text-1$ . Sample reasoning: After dividing both sides by -4, we get $y-2=\text{-}3$ . After adding 2 to both sides, we get $y=\text{-}1$ .

Responding to Student Thinking

Points to Emphasizepoints_to_emphasize

Response: If most students struggle with solving equations, plan to focus on strategies when opportunities arise over the next several lessons. For example, invite multiple students to share their thinking about which method they agree with in this activity:

Standards

Addressing

7.EE.4·Use variables to represent quantities in a real-world or mathematical problem, and construct simple equations and inequalities to solve problems by reasoning about the quantities.
7.EE.B.4·Use variables to represent quantities in a real-world or mathematical problem, and construct simple equations and inequalities to solve problems by reasoning about the quantities.