4a(6+b+2b)=

1. Combine like terms inside the parentheses: $$6+b+2b = 6+3b$$.

2. Distribute $$4a$$ to the simplified expression: $$4a \times 6 + 4a \times 3b$$.

3. Simplify: $$24a + 12ab$$.

$$24a + 12ab$$