Difficulties solving equation in Mathcad

When you say “solve” I guess you intend to solve for y’, right?

And its not just 13 - to be unit consistent it has to be 13 inches, so you must add a unit of length!!

A solve block sure should work OK if setup correctly. You definitely should attach your worksheet with the variable assignments, your equation and your tries to solve it.

I would suggest using the “root” function. It takes up less space and does the job equally well. Your equation has two solutions for y’ and I guess you are interested in the positive solution (which one you get depends an the guess value).

Here is how it looks in legacy Mathcad 15. Should work the same in Prime

Creating variable names like “y’” or “A’c” is a bit tricky and so I suggest using ‘normal” variables names without the single quotation mark (also called the prime symbol used to designate a derivative). 

P.S.: You posted in “Mathcad Installation” but should have posted in “Mathcad”.

And, yes, its confusing and not intuitive as actually the correct place is
Home>Community>Community>Mathcad>Mathcad

Having ‘Community’ as well as ‘Mathcad’ twice in that path may be quite irritating.

Maybe a kind @moderator could move your post to the correct place.
​@Catalina : Is there a generic account for moderators (and also for admins)? @moderator and @admin seem not to be valid user accounts.

EDIT: Looks like I found it → ​@PTCModerator  and also account with the same name but additionally 2, 3 and 4 at the end. Is this documented somewhere and have I overlooked it?
Did not find anything similar for admins.

Note that you could also solve the problem in a different way. Without any of the numerical values defined (And I've used Wuk to replace the strange ‘13’ which might need to be ‘13 in’) you can get a function as a result:

Now you can call that function with your parameter values, to get (all possible answers):

Success!
Luc