Answer
See below
Work Step by Step
A second dose of the drug is taken 1 hour after the first dose. We will replace every $t$ with $t-1$
$$A_1=\frac{391t^2+0.112}{0.218t^4+0.991t^2+1}\\A_2=\frac{391(t-1)^2+0.112}{0.218(t-1)^4+0.991(t-1)^2+1}$$
The total amount of aspirin in the bloodstream after the second dose is taken is given by:
$A=A_1+A_2\\=\frac{391t^2+0.112}{0.218t^4+0.991t^2+1}+\frac{391(t-1)^2+0.112}{0.218(t-1)^4+0.991(t-1)^2+1}$
