Two-Step Equations

Standards  CC.8.EE.7 Solve linear equations in one variable.

Let’s look at pg. 171  Let’s walk through the activity.  Now let’s work through number 2.

Definitions  Two-step equation- an equation that contains two operations. To solve it, you have to undo each operation in reverse order.  Coefficient- a numerical factor of a term that contains a variable.  Reflexive Property of Equality- for any numbers a and b, if a = b, then b = a. So you can switch them.

Questions:  3x = 12  How would you solve this equation?  Suppose you add 2 to each side of the equation. What is the resulting equation?  Do the equations 3x = 12 and 3x + 2 = 14 have the same solution?  What would you have to do to the equation 3x + 2 = 14 to make it look like the equivalent equation 3x = 12?

Questions  In an equation such as 3p + $2.50 = $7, which operation should be undone first? Second?

Let’s practice  2x + 3 = 7

Let’s practice  25 = ¼ n - 3

Let’s practice  6 – 3x = 21

Let’s practice  3x + 2 = 20

Let’s practice  5 + 2n = -1

Let’s practice  -1 = 1/2a + 9

Let’s practice  10 – 2/3p = 52

Let’s practice  Simon has $150 for a class trip that costs $320. He needs to save money for the next 10 weeks in order to pay for the trip. Solve the equation 10d = 320 to find the amount of money per week Simon must save.

Let’s practice  Melissa wants to put trim molding around a rectangular table. The length of the table is 45 inches and she has 150 inches of trim. Solve the equation 150 = 2w + 90 to find the width of the table.