Question 164033
the 1st term has 2 Bs and 2 As
the 2nd term has 3 Bs and 4 As
the 3rd term has 4 Bs and 6 As
the 4th term has 5 Bs and 8 As

so the nth term has (n + 1) Bs and 2n As

to find the term which has exactly 35% Bs:
(n + 1) = 35/100 * (2n + (n + 1))
<=> n + 1 = 0.35*(3n + 1)
<=> n + 1 = 1.05n + 0.35
<=> n - 1.05n = 0.35 - 1
<=> -0.05n = -0.65
<=> n = 0.65/0.05 = 13

so the 13th term has exactly 35% Bs