Missing numbers

A Puzzle

What is the missing number?

x

−

2

=

4

OK, the answer (x) is 6, right? Because 6 − 2 = 4. Easy stuff.

In Algebra we don’t use blank boxes, we use a letter (usually an x or y, but any letter is fine). So we write:

x

−

2

=

4

It is really that simple. The letter (in this case an x) just means “we don’t know this yet”, and is often called the unknown or the variable.

And when we solve it we write:

x

=

6

Why Use a Letter?

	Because:
	it is easier to write “x” than drawing empty boxes (and easier to say “x” than “the empty box”).
	if there are several empty boxes (several “unknowns”) we can use a different letter for each one.

 

Task 

• Follow the link to the missing numbers work sheet.
• Fill in the missing numbers. Use the inverse to check your answers.
• Show your workings in the box below.