1. I remmember Susan's birthday only because you reminded me about it
=> If you didn't remind me about it , so I didn't remembered Susan's birthday .

2. The car in front stopped so suddenly , so I crashed into its back
=> If the car didn't in front stopped so suddenly, so I didn't crash into it back

3. They painted the wall brown , that's why the house looked very dark
=> If the house didn't look very dark , so they didn't paint the wall brown.