The equation R=-0.0028t+20.8 can be used to predict the world record in the 200-m dash, where R is the record in seconds and t is the number of years since 1920. In what year will the record be 18.0 seconds?

The world record for the 200-m dash will be set at 18.0 seconds in the year 2920.

Step-by-step explanation:

To find what year the record will be 18 seconds, substitute 18 in for R, and solve for t.

-0.0028t + 20.8 = R

-0.0028t + 20.8 = 18

-0.0028t = - 2.8

t = 1000

The record for the 200-m dash will be 18 seconds after 1000 years. To find which year this record will be set in, add 1000 to the original date, 1920.

1920 + 1000 = 2920