Question

The sum of three time a number and 15is 42.find the number

Answer 1

Let the number be x .

This statement can be written in an equation as :-

$= \texttt{3}x \texttt{ \: + 15 = 42}$

$= \texttt{3}x \: \texttt{ = 42 - 15}$

$= \texttt{3}x \: \texttt{ = 27}$

$= x = \frac{\texttt{27}}{\texttt{3} }$

$\color{olive} =\color{olive} x \texttt{ \: \color{hotpink}= 9}$

Let us check whether or not we have found out the correct value of x, by placing 9 in the place of x :-

$=\texttt{ 3 × 9 + 15 = 42}$

$= \texttt{27 + 15 = 42}$

$= \texttt{42 = 42}$

$\hookrightarrow \: \texttt{\color{olive}LHS = \color{hotpink}RHS }$

As the left hand side of the equation is equivalent to the right hand side of the equation we can conclude that we have found out the correct value of x.

Therefore, the number is = 9