# How do you solve and check your solution given -3.4=0.4x?

Jan 7, 2018

$x = - 8.5$
... see below :)

#### Explanation:

When it says to solve, it means to find what the unknown variable equals to. So you want to isolate x to find what x is.

$- 3.4 = 0.4 x$

$- \frac{3.4}{0.4} = \frac{0.4 x}{0.4}$

$- 8.5 = x$

To check if what we got is correct, we can input the answer back into the equation. So since we found that x=-8.5, we want to replace x with -8.5

$- 3.4 = 0.4 x$

$- 3.4 = 0.4 \left(- 8.5\right)$

$- 3.4 = - 3.4$

The left side is equal to the right side, so therefore we know that our answer is correct.

Jan 7, 2018

Find a value for $x$ and then substitute it back into the original equation to see if it is true.

#### Explanation:

We are told $- 3.4 = 0.4 x$

Therefore, to begin, we need find a value for $x$. To do this we simply divide by the coefficient in front of $x$ , in this case $0.4$

$\therefore$ $\left(- \frac{3.4}{0.4}\right) = x$

$\therefore x = - \frac{17}{2}$

To check we substitute the values of $x$ back into the original equation to see if it is true.

Subbing $- \frac{17}{2}$ we get $- 3.4 = 0.4 \left(- \frac{17}{2}\right)$

which $- 3.4 = - 3.4$