Mr Davis left his reading glasses at the office so he couldn't read the newspaper at home.
If Mr Davis hadn't left his reading glasses at the office, he would have been able to read the newspaper at home.
Sophie spent all her pocket money on this T-shirt, so she didn't have any money for the weekend.
If Sophie hadn't spent all her money on this T-shirt, she would have had some money for the weekend.
Harry went to bed at 2 a.m. last night so he felt tired all day.
If Harry had gone to bed earlier last night, he wouldn't have felt tired all day.