we are given
A collector’s item is purchased for $150
so,

its value increases by 3% each year
so,

t is time in years
Let's assume cost of item after t years is C(t)
so, we can use formula

now, we can plug values


so, equation is

After doubling
C(t)=2*150=300
so, we can set C(t)=300
and then we can solve for t

we get

so, doubling time is 23.44977 years.........Answer
Graph:
we can draw graph of
