[mikeczyz]

I'll take a stab at it:

a=3000
b=343
c=.75
x=time, what we're solving for

ax=b(x+c)
ax=bx+bc
ax-bx=bc
x(a-b)=bc
x=bc/(a-b)

substitute x into ax or b(x+c) and you've got your answer.