39 is the base number, so it is the 100%
That decreased by 33 means you're looking for 67%
Easiest method is to divide the base number by 100, which gives you the 1%:
39/100 = 0.39
You now have the value of 1%, but you need 67%, so all you have to do is multiply 0.39 with 67, you get: 26.13
