Мухамед подумал о числе. Он умножил это число 2 и добавил 3, в результате чего число на 13 больше, чем он думал. О каком числе он дума помогите пожалуйста​

2. Supply the correct prepositions where necessary.
1. If I have no classes on Saturday, I'll join …you.
2. My explanation seemed strange ... the teacher.
3. … the war we were … the same front.
4. She invited me … her room.
5. He gave her a big bunch ... flowers.
6. He was on old friend … ours.
7. It was the most pleasant party … my life.
8. We tried to speak ... him, but he did not want to listen ... us.
9. You will see the New Year … … us.
10. There is a table and a few chairs … the balcony.