Let r and v be the number of socks ina regular pack and value pack, respectively. Since the store gave 6 regular packs and 5 value packs which contained 163 pair of socks, we can write

Similarly, since the store donated 6 regular packs and 4 value pack which add 146 pair of socks, we can write

Then, we have the following system of equations:

Solving by elimilation method.
By multiplying equation (b) by -1, we have an equivalent system of equations:

Then, by adding both equations, we have

Now, in order to obtain the number of socks in a regular pack, we must substitute the last result into equation (a). It yields,

which gives

By subtracting 85 to both sides, we have

Then, r is given by

Therefore, the answer is: There are 13 pairs of socks in each regular pack and 17 pairs in each value pack.