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A symbol we usually pick letters to be symbols, usually represents a number. Any letter you choose can be a variable.

A variable is a symbol that stands in for an unknown value in a mathematical expression. A variable expression is a combination of terms and mathematical operations that contains at least one variable. Example a + 2x + 10

An equation is a mathematical statement that two expressions are equal. The solution of an equation is the value that when substituted for the variable makes the equation a true statement.

Example: 3x + 5 = 14 is an equation, in which 3x+5 and 14 are two expressions separated by an ‘’equal’’ sign.

Converting the phrase into an equation:

In the left side, the phrase is ‘’ the sum of x and 10. Sum means the addition and x is the variable and the right side is 15.

Now we can write ‘’ the sum of x and 10’’ is $x+10$

The equation is $x+10=15$

Now solving the equation $x+10=15$

with proper steps localid="1649157386241" $\begin{array}{l}x+10=15\\ x+10−10=15−10\text{​â¶Ä‹}\left[\text{​â¶Ä‹Subtract10frombothsides​â¶Ä‹}\right]\text{​â¶Ä‹}\\ x=5\end{array}$

Solution of the equation is$x=5$