Solve 7x − 8 = −15

The solution of 7x − 8 = −15 is x = -1.

7x - 8 = -15\ \Rightarrow\ x = -1

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The lines y = 7x − 8 and y = -15 meet at x = -1. The solution of the equation is the x-coordinate of the point where the two sides are equal.

How to work it out

1
The goal is to get x alone. Undo the operations in the opposite order: first the subtraction, then the multiplication.
$7x - 8 = -15$
2
Add 8 to both sides:
$7x - 8 + 8 = -15 + 8 \ \Rightarrow\ 7x = -7$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{-7}{7} \ \Rightarrow\ x = -1$
4
Check: put x = -1 back into the equation.
$7\cdot(-1) - 8 = -7 - 8 = -15 \checkmark$

LaTeX source of the formulas on this page

\[ 7x - 8 = -15\ \Rightarrow\ x = -1 \]
\[ 7x - 8 = -15 \]
\[ 7x - 8 + 8 = -15 + 8 \ \Rightarrow\ 7x = -7 \]
\[ \frac{7x}{7} = \frac{-7}{7} \ \Rightarrow\ x = -1 \]
\[ 7\cdot(-1) - 8 = -7 - 8 = -15 \checkmark \]

Trying values of x in 7x − 8 = −15

x	7x − 8	Equals -15?
-3	-29	no
-2	-22	no
-1	-15	yes
0	-8	no
1	-1	no

Questions

What is x in 7x − 8 = −15?

The solution of 7x − 8 = −15 is x = -1.

How do you solve 7x − 8 = −15?

Add 8 to both sides to get 7x = -7, then divide both sides by 7 to get x = -1.

How do I check the answer?

Replace x by -1: 7(-1) − 8 = -15, which is -15.

Solve 7x − 8 = −15

How to work it out

Trying values of x in 7x − 8 = −15

Questions

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