Solve 7x − 5 = 100

The solution of 7x − 5 = 100 is x = 15.

7x - 5 = 100\ \Rightarrow\ x = 15

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The lines y = 7x − 5 and y = 100 meet at x = 15. 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.
$7x - 5 = 100$
2
Add 5 to both sides:
$7x - 5 + 5 = 100 + 5 \ \Rightarrow\ 7x = 105$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{105}{7} \ \Rightarrow\ x = 15$
4
Check: put x = 15 back into the equation.
$7\cdot15 - 5 = 105 - 5 = 100 \checkmark$

LaTeX source of the formulas on this page

\[ 7x - 5 = 100\ \Rightarrow\ x = 15 \]
\[ 7x - 5 = 100 \]
\[ 7x - 5 + 5 = 100 + 5 \ \Rightarrow\ 7x = 105 \]
\[ \frac{7x}{7} = \frac{105}{7} \ \Rightarrow\ x = 15 \]
\[ 7\cdot15 - 5 = 105 - 5 = 100 \checkmark \]

Trying values of x in 7x − 5 = 100

x	7x − 5	Equals 100?
13	86	no
14	93	no
15	100	yes
16	107	no
17	114	no

Questions

What is x in 7x − 5 = 100?

The solution of 7x − 5 = 100 is x = 15.

How do you solve 7x − 5 = 100?

Add 5 to both sides to get 7x = 105, then divide both sides by 7 to get x = 15.

How do I check the answer?

Replace x by 15: 7(15) − 5 = 100, which is 100.

Solve 7x − 5 = 100

How to work it out

Trying values of x in 7x − 5 = 100

Questions

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