21. The film was so boring that i/we couldn't watch till the end.

 S + be + so + adj + that + clause

22. The house on the corner is too expensive for us to buy.

 S + be + too + adj + ( for sb ) + to-V

23. I spend one hour and a half driving my children to school.

 spend+ V-ing 

24. She is interested in taking photos of her children

25. Taro is not interested in reading books.

 be interested in + V-ing

26. It took them half an hour to walk to the bus stop.

27. You should not spend time hanging out with him.

 waste time doing sth 

28. Girls often spend hours buying new clothes.

 waste time doing sth 

29. What about having a cup of tea.

 What about + V-ing

30. How about going to the cinema together.

 How about + V-ing

21. The film was so boring that i/we couldn't watch till the end.

 S + be + so + adj + that + clause

22. The house on the corner is too expensive for us to buy.

S + be + too + adj + to V

23. I spend one hour and a half driving my children to school.

S +  spend+ Ving 

24. She is interested in taking photos of her children
keen on + Ving = interesting in + Ving

25. Taro is not interested in reading books.

interested in + V-ing

26. It took them half an hour to walk to the bus stop.
S + took + tg + to V

27. You should not spend time hanging out with him.

 waste time + Ving  = spend + Ving

28. Girls often spend hours buying new clothes.

29. What about having a cup of tea.

What about + Ving = let's to V

30. How about going to the cinema together.
How about + Ving = Why not + S + V(HTD)