The half-life of chromium−51 is 27.8 days. how much of a 7.6−oz sample of chromium−51 will remain after 139 days?

Ending Amount = Beginning Amount / 2^n
where "n" is the number of half-lives
n = 139 / 27.8 = 5 half-lives
Ending Amount = 7.6 oz / 2^5
Ending Amount = 7.6 oz / 32
Ending Amount = .2375 ounces

Source:
http://www.1728.org/halflife.htm

The academic affairs council is the highest expert body processing academic affairs, as stipulated by the university statutes. specialist aaro häkkinen (educational policy) took part in the council’s meeting. the agenda of the meeting included bachelors’ feedback, the timing of pedagogical studies, the grant system for tuition fees, the standardisation of administrative practices for internships and the situation of foreign-language and multilingual master’s programmes.

Xis equal to three