Answer:
Let's define the variable t as the number of years that have passed since 1950.
Such that x = 0 represents the year 1950.
We know that in 1950, the record was 63.2 seconds.
And since each year since, the record has decreased by 0.4 seconds.
So we have a linear relationship:
R(t) = 63.2 s - 0.4s*t
When we have t = 0 (the year 1950)
The record is:
R(0) = 63.2s - 0.4s*0 = 63.2s
That is what we should expect.
Now, if t = 0 is the year 1950
Then t = 7 is the year 1957.
So the record in the year 1957 will be:
R(7) = 63.2s - 0.4s*7 = 60.4 seconds.
