In the hexaploid wheat, the haploid ($n$) and basic ($x$) numbers of chromosomes are:

Bread wheat ($\text{Triticum aestivum}$) is hexaploid ($6x=42$). The basic number ($x$) is the number of chromosomes in a single set, so $6x=42$ means $x=7$. The haploid number ($n$) is half the somatic number, so $n=42/2=21$.