How can you use ratios to convert units of measurement

Can someone me do math because i am having a breakdown rn because i don’t get it

The? half-life of a radioactive substance is 20 years. if you start with some amount of this? substance, what fraction will remain in 120 ? years

Harry and jay are both flying on the same plane with an airline that randomly assigns seats to passengers. of the 182 total seats on the plane, 62 are window seats, 58 are middle seats, and the rest are aisle seats. what is the approximate probability that both harry and jay will be assigned aisle seats on the same plane? a. 11.48% b. 3.3% c. 2.08% d. 26.26%