Chapter 2 - Solving Equations - 2-6 Ratios, Rates, and Conversions - Standardized Test Prep - Page 123: 45

45 times

We know that the dog's heart beats 180 times in a minute. We also know that for every four beats, the dog takes one breath. Thus, we divide 180 by 4 to obtain that the dog breathes at a rate of 45 times per minute.