Shareholders' equity and owners' equity are terms often used interchangeably in the context of a corporation. Both refer to the residual interest in the assets of the entity after deducting liabilities.
The term "owners' equity" is more general and can apply to any business structure, including sole proprietorships and partnerships, whereas "shareholders' equity" specifically refers to corporations.
Since the instruction is not to use "shareholders," "owners' equity" is the appropriate term to fill in the blank.