Simplify 2a+6b-a+2b+3a

Look for the corresponding letters to each number. So, as an example those with a. remember that the + or - before it tells us whether it is to be added or subtracted

There are 2a-a+3a so that = 4a

With b there are +6b+2b so that = 8b

In total this means a simplification is 4a+6b as both results are positive numbers.