The half-life of cesium-137 is 30 years. Suppose we have a 30 mg sample.
(a) Find the mass that remains after t years.
(b) How much of the sample remains after 20 years? (Round your answer to two decimal places.)

If the graphs of the linear equations in a system are parallel, what does that mean about the possible solution(s) of the system? a. there are infinitely many solutions. b. there is no solution. c. there is exactly one solution. d. the lines in a system cannot be parallel.

Angel entered a triathlon (a three-part race). he swam 1 mile, rode his bike 30 miles, and ran 10 miles. how far did he go altogether? a. 11 miles b. 123 miles c. 41 miles d. 40 miles

Which simplifys to a+ b? a-(1-b)+1 -(1-a)-b+1 (a--1) -1)+1