Q10. - Algebra 2

Question

 If $x=-2$, then $15-3\left(x+1\right)=$?

$\left(A\right)6 \left(B\right)12 \left(C\right)18 \left(D\right)21$

Step-by-Step Solution

Answer

The option $\left(C\right)$ is correct, the other options are incorrect, because the value of the expression $15-3\left(x+1\right)$when $x=-2$ is 18.

Step 1 – Use the substitution method to find the value of the given expression.

Substitute $x=-2$ in $15-3\left(x+1\right)$:

$\begin{array}{c}15-3(x+1)=15-3(-2+1)\text{ substitute }-2\text{ for }x\\ =15-3(-1)\text{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}simplify}\\ =15+3\\ =18\end{array}$

So, $15-3\left(x+1\right)=18$ when $x=-2$.

Step 2 – Check whether the option A is correct or incorrect.

Here, in the option $\left(A\right)$it is given that, 6.

The result in step 1 is $15-3\left(x+1\right)=18$.

So, option $\left(A\right)$is incorrect.

Step 3 – Check whether the option B is true or false.

Here, in the option $\left(B\right)$it is given that 12.

The result in step 1 is $15-3\left(x+1\right)=18$.

So, option $\left(B\right)$is incorrect.

Step 4 – Check whether the option C is true or false.

Here, in the option $\left(C\right)$it is given that 18.

The result in step 1 is $15-3\left(x+1\right)=18$.

So, option $\left(C\right)$is correct.

Step 5 – Check whether the option D is true or false.

Here, in the option $\left(D\right)$it is given that 21.

The result in step 1 is $15-3\left(x+1\right)=18$.

So, option $\left(D\right)$is incorrect.

 

Hence, the option $\left(C\right)$ is correct, the other options are incorrect, because the value of the expression $15-3\left(x+1\right)$when $x=-2$ is $18$.