Question

Solve the equation. Check your solution.

$\mathbf{18}\mathbf{-}\mathbf{r}\mathbf{=}\mathbf{42}$

Short answer

The solution for the equation$18-r=42$is$r=-24$.

Step-by-step solution

.  Separate the variable and constants

Write the original equation and separate the variables.

$\begin{array}{l}18-r=42\\ -r=42-18\end{array}$

.  Solve for r

Now, multiply both sides of the equation by -1.

$\begin{array}{l}-r\times -1=24\times -1\\ r=-24\end{array}$

Therefore, the solution of the equation is$r=-24$.

.  Check the solution 

To check the solution, write the original equation and substitute the value ofr.

$18-r=42$

Now, substitute $r=-24$and check the result.

$\begin{array}{l}18-\left(-24\right)=42\\ 18+24=42\\ 42=42\end{array}$

As the left-hand side is equal to right hand side, this signifies that the solution is correct.