You should ALWAYS attach the Mathcad/Prime worksheet, not just a picture.
Apart from that:
- In the definition for Icr, you should explicitly type a multiplication symbol *
between As' and (dc-d)
as well as between As and (d-dc).
If not As' and As are considered functions.
- If you only need numerical results, you should use the root function, or a solve block, to determine the value of dc.
Note that the symbolic processor of Mathcad/Prime does not 'know about units' by default.
But first: attach your worksheet.