Please show how to modify what follows so that it is correct.
Clear[x1, x2]
{{x1[t_], x2[t_]}} = {x1[t], x2[t]}
/. DSolve
[
{x1'[t] == 1 - 2.5 x1[t] + x2[t],
x2'[t] == 2 x1[t] - x2[t],
x1[0] == 0,
x2[0] == 0}
{x1[t], x2[t]},
t]
Plot[{x1[t], x2[t]}, {t, 0, 100}]
See attached to see the error messages .
Also it may be a good idea to have Forums dedicated to the various books on Mathematica such as "Mathematica Beyond Mathematics".
Attachments: