Solve 7x + 15 = 85

The solution of 7x + 15 = 85 is x = 10.

7x + 15 = 85\ \Rightarrow\ x = 10

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The lines y = 7x + 15 and y = 85 meet at x = 10. 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 addition, then the multiplication.
$7x + 15 = 85$
2
Subtract 15 from both sides:
$7x + 15 - 15 = 85 - 15 \ \Rightarrow\ 7x = 70$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{70}{7} \ \Rightarrow\ x = 10$
4
Check: put x = 10 back into the equation.
$7\cdot10 + 15 = 70 + 15 = 85 \checkmark$

LaTeX source of the formulas on this page

\[ 7x + 15 = 85\ \Rightarrow\ x = 10 \]
\[ 7x + 15 = 85 \]
\[ 7x + 15 - 15 = 85 - 15 \ \Rightarrow\ 7x = 70 \]
\[ \frac{7x}{7} = \frac{70}{7} \ \Rightarrow\ x = 10 \]
\[ 7\cdot10 + 15 = 70 + 15 = 85 \checkmark \]

Trying values of x in 7x + 15 = 85

x	7x + 15	Equals 85?
8	71	no
9	78	no
10	85	yes
11	92	no
12	99	no

Questions

What is x in 7x + 15 = 85?

The solution of 7x + 15 = 85 is x = 10.

How do you solve 7x + 15 = 85?

Subtract 15 from both sides to get 7x = 70, then divide both sides by 7 to get x = 10.

How do I check the answer?

Replace x by 10: 7(10) + 15 = 85, which is 85.

Solve 7x + 15 = 85

How to work it out

Trying values of x in 7x + 15 = 85

Questions

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