Answer: 36
Explanation:
From the question, we are informed that for every 4 silver cars that are sold, 6 red cards are also sold.
When there are 90 cars sold in a month, the number of silver cars that were sold would be:
= [4 / (4 + 6)] × 90
= 4/10 × 90
= 4 × 9
= 36 silver cars