I like the exercises at https://artofproblemsolving.com/alcumus https://artofproblemsolving.com/alcumus It is part of AOPS and it gives step-by-step solutions

I like the exercises at https://artofproblemsolving.com/alcumus https://artofproblemsolving.com/alcumus It is part of AOPS and it gives step-by-step solutions to problems. You need to create an account, but it is free.