How do you evaluate #(- 95) - ( - 68) + 39+ 4#?

1 Answer





When we subtract a negative number, we end up adding. I'll describe this using cold cubes (each one makes the temperature 1 degree colder) and hot cubes (each one makes the temperature 1 degree hotter):

Let's say we have a place where there are a bunch of cold cubes and a bunch of hot cubes and together the temperature is #-95#. Our first operation is to take away (subtract) 68 cold cubes (we know they are cold because of the negative sign). When we take away cold cubes, which way does the temperature move? It'll go up. And so:


The next operation says to add 39 hot cubes. The temperature will go up again:


And we add 4 more hot cubes: