Calculations with Negative Numbers

Question: What is the value that satisfies -4 + ? = -10 ?

Further Explanation

It is important to realise that there is no guessing, no doubts but straightforward logic. Here we can associate the meaning owning when the quantity is positive and owing if it negative. Also, as before, we associate the minus sign with opposite.

In this example,

I start by owing 4 ( i.e. the '- 4 ' )

What is this '+?' that must have happened if I ended up 'owing 10' ? ( i.e. the ' - 10 ')

Another debt of 6 must have been added to my plight

We write 'adding a debt of 6' as ' + ( -6) '

So in - 4 + ? = - 10 the ? must be - 6

This is equivalent to the use of a number line as shown above; it does not matter which way you argue as long as you get the logic correct!