Answer:
Probably the easiest way to visualise negative and positive numbers is using a number line, a tool with which you may well be familiar, especially if you have children at primary school.
It looks something like this:
Number line showing a scale of -25 to +25.
A number line can help you to visualise both positive and negative numbers and the operations (adding and subtracting) that you can do with them.
When you have an addition or subtraction to calculate, you start at the first number and move the second number of places either to the right (for an addition) or left (for a subtraction).
This number line is a simplified version, but you can draw them with every number included if you wish. The big advantage of a number line is that it is very easy to draw for yourself on the back of an envelope or a piece of scrap paper, and it is also quite hard to go wrong with the calculation. As long as you are careful to count the number of places that you are moving, you will reach the correct answer.