Question 1064679
.
This problem is NOT about the system of equations.


It is solved using ONE equation:


160 + 7w = 210 + 5w,


where w is the number of weeks.


<pre>
The solution is 

7w - 5w = 210 - 160,

2w = 50,

w = {{{50/2}}} = 25.
</pre>

<U>Answer</U>.  After 25 weeks.