Tom appears to be worried ( appears to be worried -сложное подлежащее) about something.
You seem to know ( seem to know-сложное подлежащее) a lot of people.
My English seems to be ( seems to be -cложное подлежащее) better.
They claim to have solved ( claim to have solved- сложное подлежащее) the problem.
David tends to forget things.( tends to forget-сложное подлежащее)