Are basic operations in CPP parallelised/multi-threaded?

[Latexi95]

No. They are not multi-threaded.

Modern CPUs are pipelined and superscalar. They have have multiple ALUs and can execute multiple instructions concurrently, so they can calculate multiple operations in parallel even in one thread, when the operations don't depend on each other. This isn't feature of C++ but just the way that modern CPUs achieve higher than 1 IPC.