Solve equation for variable
i) 3^4x-5=38
ii) 10-8(1/2)^x=5
iii) Population of Kenya was 39.8 million in 2009 and has been increasing by about 2.6% each year. If trend continues, when will population increase 45 million?
iv) Scientist starts with 100 mg of the radioactive substance. After four hours, it has decayed to 80 mg. How long after process started will it take to decay to 15 mg?