The half life of radium is 1690 years if 80 grams are present now how much will be present in 830 years?

Given that (x-3) is a factor of f(x)=x^3+ax^2-x-6, find a and hence the number of real roots or the equation f(x)=0

List the 10 possible samples (without replacement) of size 3 3 that can be obtained from the population of five officials.

Describe the symmetry of the figure. identify lines of symmetry, if any. find the angle and the order of any rotational symmetry.