Answer:
To find the number of weeks, we need to divide the interest amount ($900 - $850 = $50) by the interest rate. To convert the interest rate to a decimal, we need to divide it by 100, so 200% ÷ 100 = 2. The number of weeks can then be calculated as:
$50 ÷ ($850 x 2) = $50 ÷ $1700 = 0.029411765
To find the number of weeks, we need to take the reciprocal of this value, which is approximately 34.15 weeks.