Answer:
n = 1.40 (second option)
The choice second;
[tex]n = 1.40[/tex]
Step-by-step explanation:
[tex]0.7n + 0.8n = 2.1 \\ 1.5n = 2.1 \\ \\ n = \frac{2.1}{1.5} \\ \\ n = \frac{21}{15} \\ \\ n = 1.4[/tex]
I hope I helped you^_^
