Math CentralQuandaries & Queries


Question from Jessica, a student:


Hi Jessica.

Think of "x" as replacing a very particular thing: like the cost of a ticket to a movie. So

2 tickets + 3 tickets = $30.

What do you get when you add 2 tickets plus 3 tickets? You get 5 tickets, of course. So

2x + 3x = 5x.

This means 5x = 30, or 5 tickets = $30.

Now to find the cost of just 1 ticket, we have to decide how to get x by itself. Since 5x ÷ 5 = x, we can get x by dividing by 5.

So we have to divide both sides of the equation by 5. (This is very important! If you want to change one side of an equation, you have to change the other side the same way.)

5x ÷ 5 = 30 ÷ 5

x = 6.

(In our example, the tickets cost $6 each).

Stephen La Rocque. >

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