are you sure the first equation is correct because when you plug in 50 it gives you 1238392 for the yr 2000 pop and not 1238415.
and same with the second equation, it doesnt agree with the data when you plug in 10.
the equation has gradient m=(y'-y)/(x'-x)
then y=mx+c where c is a constant etermined by plugging in a value.
( 0, 1113915 ) ( 10, 1238415 )
gradient is (1238415-1113915)/(10-0)=12450
x=0 gives y=c=1113915
so equation is y=12450x+1113915
i think maybe you mistyped 12450 and wrote 112450 by accident.
( 0, 533242 ) and ( 50, 1238415 )
now try them