An unknown radioactive element decays into non-radioactive substances. In 240 days the radioactivity of a sample decreases by 68 percent. What is the half-life of the element?

One of the same side angles of two parallel lines is 20° smaller than the other one. find the measures of these two angles.

Someone answer asap for ! the boiling point of water at an elevation of 0 feet is 212 degrees fahrenheit (°f). for every 1,000 feet of increase in elevation, the boiling point of water decreases by about 2°f. which of the following represents this relationship if b is the boiling point of water at an elevation of e thousand feet? a. e = 2b - 212 b. b = 2e - 212 c. e = -2b + 212 d. b = -2e + 212

Assume that y varies inversely with x. if y=1.6 when x=0.5 find x when y=3.2