Rick had $20. He spent $10 on food, $6 on a movie ticket, and saved the rest. ( Pls answer both questions )

A. How much money did he save ?
B. What fraction of the total amount did he save ?

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.

3/4 = c/36 i need with this fraction proble.

Ineed with question three. i don't understand how i'm supposed to achieve 3 marks.