Looking at the chart we can see that there were 6 days with a temperature below 70 and with rain.
If you add all the numbers in the chart you get a total of 6 + 2 + 14 + 8 = 30 days
Now that we know the total number of days and the days to find a percentage for, we can find the percentage by dividing those specified days by the total (specified days/total days) and multiplying by 100 to get the answer in percentage form
So set up a fraction where (6 / 30) * 100 is the percent