Question

Supriya asked Neeti to think of a number. Then she asked to double it and add $5$ to it. If the result was $21$, what number did Neeti think?

Answer 1

Let the number be $\mathrm{x}$

So double of $\mathrm{x}$ is $2\mathrm{x}$

Now, by adding $5$ to it, we get $2\mathrm{x}+5$

Now according to given condition ,

$$\begin{gathered} \Rightarrow 2\mathrm{x}+5=21 \\ \Rightarrow 2\mathrm{x}=21-5 \\ \Rightarrow 2\mathrm{x}=16 \\ \Rightarrow \mathrm{x}=\frac{16}{2} \\ \Rightarrow \mathrm{x}=\frac{{\displaystyle \stackrel{8}{\cancel{16}}}}{\cancel{2}} \\ \Rightarrow \mathrm{x}=8 \end{gathered}$$

Hence, Neeti thought of number $8$.