How to make the program use MPa instead of Pa in the formula?
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How to make the program use MPa instead of Pa in the formula?

Engineering formulas should be unitless, as is from books.
In the empty place holder of Q, paste MPa from user unit.

The topic starter has used units just the way it is efficient in SMath Studio. Write a formula as found in a book, define the quantities using the given units and get the result in the correct dimension.
If you don't like the default unit, you can change the display easily.

Go to the unit placeholder and type the desired result there. The dynamic assistant will help with a list of known items. In the given case it is sufficient to type MP and then TAB to confirm the selection in the list.



Read more on this in the "Units of measurement" branch of the Interactive handbook.

The program does not use the number I need.
if I choose "Ignore units" the program solves correctly

Often these types of formulas are made to be used with specific units as input... my thought is that the 10^6 used in the denominator is specifically provided to use P.a in MegaPascal as input, while the program uses the base units (the ratio under the arrow has P.a in either numerator and denominator, thus the magnitude doesn't matter here, unless you provide P.пр and P.a with wrong relative magnitude)