Which relations represent a function?

a.
(16, 14)
(14, −12 )
(9, 11)
(10, 14)

b.
(10, 8)
(7, 9 )
(9, 13)
(8, 5)

c.
(18, 24)
(16, 10 )
(5, 13)
(18, 14)

d.
(14, 12)
(10, 12 )
(−13, 7)
(11, 15)

Apatient is given 50 mg dose of medicine the medicines effectiveness decreases every hour at a constant rate of 40% what is the exponential decay function that models this scenario how much medicine will be left in the patients system after 2 hours

Reinel saves 30% of every pay check. his paycheck last week was 560$. how much did reniel save last week?

In july, the average temperature in one us city was 29°c. by december, the average temperature had fallen by 29°c. explain why the average temperature in december was 0°c.