Final answer:
The number of white shirts sold is 54.
Step-by-step explanation:
To solve this problem, let's represent the number of blue shirts as x. Since the shop sells 6 times as many white shorts as blue shirts, we can represent the number of white shorts as 6x. According to the problem, there are 63 shirts in total, so we have the equation x + 6x = 63. Simplifying this equation yields 7x = 63. Dividing both sides of the equation by 7 gives us x = 9. So, the number of white shirts sold is 6x = 6(9) = 54.