Question

if 85% of an aspirin remains in the bloodstream after 3.0 h, how long after an 80 mg aspirin is taken does it take for there to be 35 mg in the blood stream?

Answer 1

Aspirin consumed 15 % in 3 hrs

35 mg out of 80 mg  is =  43.75%

Time duration : $\frac{3 hours}{15}* 43.75 = 8.75 hours$