In 1992 the life expectency of males in a certain counrty was 73.4 years. In 1999 it was 76.7 years. Let E represent the life expectancy in years t and let t represent the number of years since 1992.

Answer 1

Are we to assume that the increase follows a linear function, i.e., it can be expressed by a straight line graph?
if so, then

treat your data as two ordered pairs
(0,73.4) and (7,76.7)

slope = (76.7-73.4)/(7-0) = 3.3/7 = 33/70

so y = (33/70)t + b
but (0,73.4) is the y-intercept or b

so y = (33/70)t + 73.4

Answer 2

here from 2021