When making equivalent fractions where you have both denominators and only one numerator, see if the smaller denominator goes into the larger denominator equally. In this case, 25*4=100, so 25 does go in equally. This means that your first fraction, 8/25, grows times 4 to your second fraction, ?/100. So, to figure out ?, since you multiply 25 by four to get 100, you would multiply 8 by four to get ?.
8*4=32
So...
8/25=32/100
And there's your answer.
