To simplify the expression, combine like terms. Like terms have the same variable raised to the same power.
Group the 'a' terms: 5a - 2a = (5 - 2)a = 3a
Group the 'b' terms: 3b + b = 3b + 1b = (3 + 1)b = 4b
Combine the simplified terms: 3a + 4b
So, the simplified expression is 3a + 4b.