Helllp I cant answer and more questions

Find an bif a = {3, 6, 9, 12) and b = {2, 4, 6, 8, 10).

Suppose a laboratory has a 30 g sample of polonium-210. the half-life of polonium-210 is about 138 days how many half-lives of polonium-210 occur in 1104 days? how much polonium is in the sample 1104 days later? 9; 0.06 g 8; 0.12 g 8; 2,070 g

A+b= 17, ab=70, find the value of |a-b|