Tiffany is packing her bags for her vacation, she has 8 unique pairs of shoes but only 4 fit how many different groups of 4 shoes can she take

Fractions can be added and subtracted only if they're fractions. a. like b. proper c. improper d. unlike

Anyone know? will mark brainliest if correct

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.