How do you simplify #a + 2c - 5b - c + a - b #?
This is addition of algebraic terms.
In Algebra we may only add terms that are like (the same).
There are 6 terms - we can re-arrange them to have the like terms together. The terms are usually arranged in alphabetical order.
We only add the numerical coefficients (the numbers in front of the terms) and keep the variables the same.
Remember that if no number is written it means there is 1.