algebra
posted by need help please on .
ok i don't get this one
in 1920 the record for a certain race was 45.9 sec in 1980 it was 44.1 sec let r (T) = the record in the race and t= the number of years since 1920
(a) find a linear fuction that fits the data
(b) use the funcation in (a) to perdict the record for 2003 and 2006
(c) find t he year when the record will be 43.20 sec..
help please thatnks in advance

r = m (t) + b
when year = 1920, t = 0
where t = year  1920
45.9 = m (0) + b
so b = 45.9
44.1 = m (19801920) + 45.9
44.1 = 60 m + 45.9
60 m = 1.8
m = .03
so
r =.03 t + 45.9
when year = 2003
t = 2003  1920 = 83
r = .03 (83) + 45.9
r = 43.41
that should get you started 
so what yr will it be 43.20

so r(t)=?

as I said
r =.03 t + 45.9
then
43.2 = .03 t + 45.9
.03 t = 2.7
t = 90
1920 + 90 = 2010