5.A hobby store is having a promotion on picture frames: buy 3 get the 4th frame at 75% off. Write an expression to represent the total cost for 4 frames in two different ways.

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