7. 1990-2006,showsthenumberofpairs, e(t), can be represented by the function e(t) = 204(1.04)t, where t represents the number of years since the study began.

Well, the give us 1990-2006 as the time period. If you don't know how many years that is and don't feel like counting: 2006-1990=16

Then plug it in the equation t=16
E(t)=204(1.04)t
E(16)=204(1.04)16
E(16)=212.16•16
E(16)=3394.46