"Simple as ABC" is a common phrase used to describe tasks or concepts that are basic, straightforward, and easy to understand. There are several synonyms for this phrase that can be used to express the same idea, such as "easy-peasy," "piece of cake," "child's play," "a walk in the park," "smooth sailing," "plain sailing," "a breeze," "effortless," and "simple as pie." These synonyms emphasize that the task at hand requires a minimal amount of effort or skill, and can be completed with ease. Using these phrases can add variation to your writing or conversations, and can also help convey the simplicity of a particular task or concept.