Answer:
10.1%
Explanation:
The first thing we should do is calculate the total volume of the solution when mixing them would be: 
0.7 + 0.3 = 1 
Now, we have that the resulting concentration (x) would be equal to the sum of the multiplications between the volumes and the concentrations to be mixed, as follows: 
x * 1 = 0.7 * 0.05 + 0.3 * 0.22 
x = 0.035 + 0.066 
x = 0.101 
That is, the concentration of the resulting mixture would be 10.1% (0.101 * 100)