Example

Solving 7x+8=137x + 8 = -13 by Collecting Constants

To solve 7x+8=137x + 8 = -13, begin by identifying which side of the equation holds the variable term. Because 7x7x appears only on the left, designate the left as the variable side and the right as the constant side.

Step 1 — Remove the misplaced constant from the variable side: The constant 88 is on the variable side, so subtract 88 from both sides using the Subtraction Property of Equality:

7x+88=1387x + 8 - 8 = -13 - 8

7x=217x = -21

Now all variable terms are on the left and only a constant remains on the right.

Step 2 — Isolate the variable using the Division Property of Equality: Because xx is multiplied by the coefficient 77, divide both sides by 77:

7x7=217\frac{7x}{7} = \frac{-21}{7}

x=3x = -3

Step 3 — Check by substitution: Replace xx with 3-3 in the original equation:

7(3)+8=?137(-3) + 8 \stackrel{?}{=} -13

21+8=?13-21 + 8 \stackrel{?}{=} -13

13=13-13 = -13 \checkmark

Because both sides are equal, x=3x = -3 is confirmed as the correct solution. This example shows that when the variable appears on only one side of the equation, any constants on that same side must first be moved to the opposite side before the coefficient can be divided away.

0

1

Updated 2026-04-21

Contributors are:

Who are from:

Tags

OpenStax

Elementary Algebra @ OpenStax

Ch.2 Solving Linear Equations and Inequalities - Elementary Algebra @ OpenStax

Algebra

Math

Prealgebra

Related
Learn After