Solve 7x − 4 = 87

The solution of 7x − 4 = 87 is x = 13.

7x - 4 = 87\ \Rightarrow\ x = 13

Explain it step by step in chat Make a short video of it

The lines y = 7x − 4 and y = 87 meet at x = 13. 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.
$7x - 4 = 87$
2
Add 4 to both sides:
$7x - 4 + 4 = 87 + 4 \ \Rightarrow\ 7x = 91$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{91}{7} \ \Rightarrow\ x = 13$
4
Check: put x = 13 back into the equation.
$7\cdot13 - 4 = 91 - 4 = 87 \checkmark$

LaTeX source of the formulas on this page

\[ 7x - 4 = 87\ \Rightarrow\ x = 13 \]
\[ 7x - 4 = 87 \]
\[ 7x - 4 + 4 = 87 + 4 \ \Rightarrow\ 7x = 91 \]
\[ \frac{7x}{7} = \frac{91}{7} \ \Rightarrow\ x = 13 \]
\[ 7\cdot13 - 4 = 91 - 4 = 87 \checkmark \]

Trying values of x in 7x − 4 = 87

x	7x − 4	Equals 87?
11	73	no
12	80	no
13	87	yes
14	94	no
15	101	no

Questions

What is x in 7x − 4 = 87?

The solution of 7x − 4 = 87 is x = 13.

How do you solve 7x − 4 = 87?

Add 4 to both sides to get 7x = 91, then divide both sides by 7 to get x = 13.

How do I check the answer?

Replace x by 13: 7(13) − 4 = 87, which is 87.

Solve 7x − 4 = 87

How to work it out

Trying values of x in 7x − 4 = 87

Questions

Similar equations