-4m - 12m - 3 + (m - 1.5) =

Combine like terms on the left side of the expression.

Step 1: Remove the parentheses: -4m - 12m - 3 + m - 1.5.

Step 2: Combine the 'm' terms: (-4 - 12 + 1)m = -15m.

Step 3: Combine the constant terms: -3 - 1.5 = -4.5.

Step 4: The simplified expression is -15m - 4.5.