1. ## Solve for x

In school we started doing algebra but I don't know where to begin with , can someone help me please?
Thanks
5x=15

2. ## Re: Solve for x

If it's a simple solve for x, it would be 15/5=3

Some textbooks might be useful for homework help. If your school has prescribed some, just use those. Frequently getting some help from a senior might also help. Asking your teacher to explain again, should not be an issue. Most teachers are happy to help.

3. ## Re: Solve for x

the key rule in algebra is anything you do to one side of the equation you must do to the other side of the equation.

$5x = 15$

here we would like to isolate the $x$ on one side of the equation.

Let's multiply both sides by $\dfrac 1 5$

$\dfrac 1 5 \cdot 5 x = \dfrac 1 5 \cdot 15$

$x = 3$

and voila!

4. ## Re: Solve for x

In school we started doing algebra but I don't know where to begin with , can someone help me please?
5x=15
5 apples cost 15 cents...

5. ## Re: Solve for x

Think of it as "something has been done to x and to get back to x, we have to 'undo' it". And "undoing" a mathematical operation means doing the opposite (technically the "inverse"). In 5x= 15, x has been multiplied by 5. The "opposite" of "multiply by 5" is "divide by 5" (or equivalently, as romsek said, "multiply by 1/5"). And, of course, to keep the two sides equal, whatever you do to one side of an equation you have to do to the other.

6. ## Re: Solve for x

A math teacher wrote down 5 * 3 = 15

He then removed the 3 and replaced it with letter x to end up with 5 * x = 15

He then gave that to Basko and asked him to calculate what number the x represented