Verified answer

Solution:

Let the number added be a.

According to the question, we have:

[tex] \tt2( \frac{ - 7}{3} ) + a = \frac{3}{7} [/tex]

[tex] \tt \frac{ - 14}{3} + a = \frac{3}{7} [/tex]

[tex] \tt{a = \frac{3}{7} + \frac{14}{3} }[/tex]

[tex] \tt{a = 9+ \frac{98}{21}} [/tex]

[tex] \tt a = \frac{107}{21} [/tex]

Final Answer:

So the number that must be added to twice rational number -7/3 to get 3/7 is 107/21.