Answer: [tex]F=0.41w[/tex]
Step-by-step explanation:
1. You know that the force F varies directly as the weight w of the sofa. Then, you can write the following expression:
[tex]F=kw[/tex]
Where k is the constant of proportionality.
2. You know that a person can push a 120 pound sofa with a force of 50 pounds, then you can calcualte the constant of proportionality as following:
[tex]k=\frac{F}{w}=\frac{50lb}{120lb}=0.41[/tex]
3. Then, the equation is:
[tex]F=0.41w[/tex]