Solve 7x − 8 = 90

The solution of 7x − 8 = 90 is x = 14.

7x - 8 = 90\ \Rightarrow\ x = 14

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The lines y = 7x − 8 and y = 90 meet at x = 14. 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.
$7x - 8 = 90$
2
Add 8 to both sides:
$7x - 8 + 8 = 90 + 8 \ \Rightarrow\ 7x = 98$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{98}{7} \ \Rightarrow\ x = 14$
4
Check: put x = 14 back into the equation.
$7\cdot14 - 8 = 98 - 8 = 90 \checkmark$

LaTeX source of the formulas on this page

\[ 7x - 8 = 90\ \Rightarrow\ x = 14 \]
\[ 7x - 8 = 90 \]
\[ 7x - 8 + 8 = 90 + 8 \ \Rightarrow\ 7x = 98 \]
\[ \frac{7x}{7} = \frac{98}{7} \ \Rightarrow\ x = 14 \]
\[ 7\cdot14 - 8 = 98 - 8 = 90 \checkmark \]

Trying values of x in 7x − 8 = 90

x	7x − 8	Equals 90?
12	76	no
13	83	no
14	90	yes
15	97	no
16	104	no

Questions

What is x in 7x − 8 = 90?

The solution of 7x − 8 = 90 is x = 14.

How do you solve 7x − 8 = 90?

Add 8 to both sides to get 7x = 98, then divide both sides by 7 to get x = 14.

How do I check the answer?

Replace x by 14: 7(14) − 8 = 90, which is 90.

Solve 7x − 8 = 90

How to work it out

Trying values of x in 7x − 8 = 90

Questions

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