question about suggested article

In the explanation that the article “Water Model Calibration Tips” wiki à https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/40028/water-model-calibration-tips

 

There is an article called; “Model Calibration Data: the good , the bad, and the useless”

In that article the following is stated:

“The Hazen-Williams equation can be solved for C-factor to give
 (1)” (p.96)

I understand why the “error” element is introduced since the article is usig the equation to highlight the impact of errors on C factors that might result from calibration. However on the “Bentley WaterGEMS CONNECT Edition Help” website à https://docs.bentley.com/LiveContent/web/Bentley%20WaterGEMS%20SS6-v1/en/GUID-E5FCE3A52CBA40899062D149A5CE2D5A.html

The Hazen Williams equation is described as follows:

 

Q

=

Discharge in the section (m 3 /s, cfs)

 

C

=

Hazen-Williams roughness coefficient (unitless)

 

A

=

Flow area (m 2 , ft. 2 )

 

R

=

Hydraulic radius (m, ft.)

 

S

=

Friction slope (m/m, ft./ft.)

 

k

=

Constant (0.85 for SI units, 1.32 for US units).

If I try to isolate for C using this equation I do not see how I get to: