*FIRST PERSON TO GET IT RIGHT AND ANSWER FIRST GETS BRAINLIEST* In an aquarium, there are starfish and octopi in a tank. The total number of animals in the tank is 30. The total number of legs in the tank is 171. Assuming that all animals have all their legs, find the number of each type of animal in the tank. (Starfish have 5 legs and Octopus have 8 legs)

(solve using substitution method. MUST SHOW WORK)

Ariana starts with 100 milligrams of a radioactive substance. the amount of the substance decreases by 20% each week for a number of weeks, w. the expression 100(1−0.2)w finds the amount of radioactive substance remaining after w weeks. which statement about this expression is true? a) it is the difference between the initial amount and the percent decrease. b) it is the difference between the initial amount and the decay factor after w weeks. c) it is the initial amount raised to the decay factor after w weeks. d) it is the product of the initial amount and the decay factor after w weeks.