Substance decays at a rate of 0.9%. what is the half life?

Tracy solved the following problem. which of the statements is true? 9 ÷ 3 + 6 × 2 3 + 6 × 2 9 × 2 18 her answer is correct. her answer is incorrect. she should have multiplied before dividing. her answer is incorrect. she should have multiplied before adding. her answer is incorrect. she should have added before dividing.

The total number of dental clinics total for the last 12 months was recorded

Do you mind if you guys me with this question i’m on number 8