Solve 2x + 15 = 51

The solution of 2x + 15 = 51 is x = 18.

2x + 15 = 51\ \Rightarrow\ x = 18

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The lines y = 2x + 15 and y = 51 meet at x = 18. 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.
$2x + 15 = 51$
2
Subtract 15 from both sides:
$2x + 15 - 15 = 51 - 15 \ \Rightarrow\ 2x = 36$
3
Divide both sides by 2:
$\frac{2x}{2} = \frac{36}{2} \ \Rightarrow\ x = 18$
4
Check: put x = 18 back into the equation.
$2\cdot18 + 15 = 36 + 15 = 51 \checkmark$

LaTeX source of the formulas on this page

\[ 2x + 15 = 51\ \Rightarrow\ x = 18 \]
\[ 2x + 15 = 51 \]
\[ 2x + 15 - 15 = 51 - 15 \ \Rightarrow\ 2x = 36 \]
\[ \frac{2x}{2} = \frac{36}{2} \ \Rightarrow\ x = 18 \]
\[ 2\cdot18 + 15 = 36 + 15 = 51 \checkmark \]

Trying values of x in 2x + 15 = 51

x	2x + 15	Equals 51?
16	47	no
17	49	no
18	51	yes
19	53	no
20	55	no

Questions

What is x in 2x + 15 = 51?

The solution of 2x + 15 = 51 is x = 18.

How do you solve 2x + 15 = 51?

Subtract 15 from both sides to get 2x = 36, then divide both sides by 2 to get x = 18.

How do I check the answer?

Replace x by 18: 2(18) + 15 = 51, which is 51.

Solve 2x + 15 = 51

How to work it out

Trying values of x in 2x + 15 = 51

Questions

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