Question

In the following exercises, solve each number word

The difference of four times a number and seven is $21$. Find the number.

Short answer

The number is $7$.

Step-by-step solution

Step 1. Given Information  

We are given that the difference of four times a number and seven is $21$.

We have to find the number.

Step 2. Forming the equation  

Let the number bex,

So, the equation will be,

$4x-7=21$

Step 3. Solving the equation  

Adding $7$from both sides, we get

$$\begin{gathered} 4x-7=21 \\ 4x=21+7 \\ 4x=28 \end{gathered}$$

Dividing by $4$,

$$\begin{gathered} x=\frac{28}{4} \\ x=7 \end{gathered}$$

Hence, the number is $7$.

Step 4. Checking the solution 

Putting the value of xin the equation, we get

$$\begin{gathered} 4x-7=21 \\ 4\left(7\right)-7=21 \\ 28-7=21 \\ 21=21 \\ LHS=RHS \end{gathered}$$

Hence the solution is correct.