If y varies jointly as x and z and inversely as the square of w, and y = 3 when x = 3, Z = 10, and w = 2, then y = 4 when x = 4, z = 20, and w= 4. True or False ?

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