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1. 5 - 8 / 5 × 100 = 60
From $5 to $8 is 60% increase.
2. 20 - 30 / 20 × 100 = 50
From 20 students to 30 students is a 50% increase.
3. 86 - 150 / 86 × 100 = 74.4186046511628 Round to 74.
From 86 books to 150 books is a 74% increase.
4. 3.49 - 3.89 / 3.49 × 100 = 11.461318051575958 Round to 11.
From $3.49 to $3.89 is 11% increase.