Question

Priya spends $42 a week on coffee and donuts across 5 days. She

Answer 1

If she spends $42 a week on coffee and every day she spends the same amount (I don't see this in the question, only doughnuts.), then $30 can get her 30 : 42 = 5/7 of a week of coffee -> 5 days.

So, she spends 5 days on coffee -> she must also spend 5 days on doughnuts

And since she spends 30 dollars equally everyday, she spends 30 : 5 = $6 everyday on doughnuts