Questions & Answers about Багетная мастерская открыта.
Because открыта is the short form of the adjective открытый and is commonly used in Russian to mean is open in a predicate:
- Мастерская открыта. = The workshop is open.
The long form открытая usually describes a noun directly:
- открытая мастерская = an open workshop
So in this sentence, открыта means the state of the workshop, not just a permanent descriptive quality.
It agrees with мастерская, which is feminine singular.
Short-form adjectives change by gender and number:
- masculine: открыт
- feminine: открыта
- neuter: открыто
- plural: открыты
Since мастерская is feminine, you get открыта.
Yes—if you think in English terms, there is an implied is.
Russian normally omits to be in the present tense:
- Багетная мастерская открыта. = The baguette/framing workshop is open.
There is no present-tense word like is in ordinary Russian sentences of this type.