The first sentence of the question gives you the numbers; the second asks the question. Plugging in $17.57 million for the repurchased stock and $35.10 billion for the market value, the question can be rephrased as: What percent of $35.10 billion is represented by $17.57 million? That's a ratio. Approximate so that the numbers work out easily:

17.5 million divided by 35 billion, times 100 percent:

(17,500,000 / 35,000,000,000) x 100%
= (17.5 / 35,000) x 100%
= 1,750 / 35,000
= 17.5 / 350 = 1/20 = 0.05%