Answer
2.8 days,
$(2.8, 50)$
Work Step by Step
Insert $P(x)=40$ and solve for x.
$40=95-30\log_{2}x\qquad.../-40+30\log_{2}x$
$30\log_{2}x=45\qquad.../\div 30$
$\log_{2}x=1.5\qquad...$apply $2^{(...)}$ to both sides
$ x=2^{1.5}\approx$2.82842712475$\approx 2.8$ days
After 2.8 days, only half the students recall...
Since $P(2.8)=50,$ the point on the graph is $(2.8, 50)$
