How to add two equations in c...
I was given a hint i.e. to use sscanf and printf......

You probably need to be a bit more detailed about what it is that you're trying to do here. For example, what do you mean by "add two equations"? Also, you're more likely to get some useful advice if you've attempted to write some code, but it has a problem that you can't understand how to solve. So, if you've written something already then you can post it here (make sure that you use [ code ] tags, so it's easier for people to see what's going on) and maybe we can sort out your problems.