How do I simplify the algebraic expression 5a + 3b − 2a + b?

You can only combine 'like terms', which are terms that have exactly the same letter part. In 5a + 3b − 2a + b, the terms 5a and −2a are like terms because both have 'a', and 3b and b are like terms because both have 'b'. Group them: (5a − 2a) + (3b + b). Now add the number coefficients of each group: 5a − 2a = 3a, and 3b + b = 4b (remember b on its own means 1b). So the simplified expression is 3a + 4b. You cannot combine 3a and 4b any further because a and b are different unknowns, like apples and bananas. Always keep the letter the same when you add or subtract coefficients.