the number of kilograms of water in a human body varies directly as the mass of the body. an 87-kg person…

Explanation:

Step1: Define direct variation

Let $w$ = water mass, $m$ = body mass. Direct variation: $w = km$, where $k$ is constant.

Step2: Solve for $k$

Substitute $w=58$, $m=87$: $k = \frac{w}{m} = \frac{58}{87} = \frac{2}{3}$

Step3: Calculate water for 75-kg person

Substitute $m=75$, $k=\frac{2}{3}$: $w = \frac{2}{3} \times 75$

Answer:

50 kg of water are in a 75-kg person.