You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Dissolution_of_the_Soviet_Union

Context:
In the fall of 1985, Gorbachev continued to bring younger and more energetic men into government. On September 27, Nikolai Ryzhkov replaced 79-year-old Nikolai Tikhonov as Chairman of the Council of Ministers, effectively the Soviet prime minister, and on October 14, Nikolai Talyzin replaced Nikolai Baibakov as chairman of the State Planning Committee (GOSPLAN). At the next Central Committee meeting on October 15, Tikhonov retired from the Politburo and Talyzin became a candidate. Finally, on December 23, 1985, Gorbachev appointed Yeltsin First Secretary of the Moscow Communist Party replacing Viktor Grishin.

Question:
Who was Chairman of the Council of Ministers prior to Ryzhkov?

Nikolai Tikhonov