Question

How do you solve $3x+9=21$ ?

Answer 1

Hint: In this question, we have to find the value of x. As we have to solve a linear equation that consists of only a variable. Thus, we will apply simple mathematical operations to get the solution to the problem. Therefore, we start solving this equation by subtracting 9 on both sides of the equation and then we cancel out the same terms with the opposite sign on the left-hand side of the equation. Then, we will again divide 3 on both sides of the equation and make the necessary calculations that give the value of x, which is our required answer.

Complete step by step answer:
According to the question, we have to find the value of x.
The equation given to us is $3x+9=21$ ---------- (1)
First, we will subtract 9 on both-hand sides of the equation (1), that is
$\Rightarrow 3x+9-9=21-9$
Now, we know that the same terms with opposite signs cancel out each other, therefore we cancel the same terms on the left-hand side in the above equation, we get
$\Rightarrow 3x=12$
Now, we will divide 3 on both sides in the above equation, we get
$\Rightarrow \dfrac{3}{3}x=\dfrac{12}{3}$
On further solving the above equation, we get
$\Rightarrow x=4$ which is our required answer.

Therefore, for the equation $3x+9=21$ , the value of x is equal to 4, which is our required answer.

Note: Make all the necessary calculations properly and avoid mathematical errors. Do write all the steps one-by-one to avoid any mistakes. One of the alternative methods to solve this problem is subtracting 21 on both sides of the equation and then makes the necessary calculations. After that we will add 12 on both sides of the equation and simplify the equation, to get the value of x, which is our solution.