Who becomes president if the 25th amendment is invoked

The vice president

Explanation:

The 25th amendment was made to solve the problem of who becomes president if the current president is unable to fulfill their duties. The amendment states, "if the President becomes unable to do his job, the Vice President becomes the President or Acting President." With "acting president" means that the vice president will only have the title/power for a limited time. The 25th amendment may be invoked if the president dies or is unconscious for an amount of time. The first will result in the vice president becoming president and the latter will cause the vice president to become the acting president.

The 25th amendment was recently invoked when President Biden underwent a medical procedure. Kamla Harris then became acting president for a few hours.