Erika assembling $9$ calculators is the same as assembling three groups of $3$ calculators. Since Erika assembles $3$ calculators in the same amount of time that Nick assembles $2$ calculators, then he assembles three groups of $2$ calculators (that is, $6$ calculators) in this time. Since Nick assembles $1$ calculator in the same amount of time that Sam assembles $3$ calculators, then Sam assembles $18$ calculators while Nick assembles $6$ calculators. Thus, the three workers assemble $9+6+18=33$ calculators while Erika assembles $9$ calculators.
