So what you do is see all the denomenators and factor them (denomenaotrs are the bottom numbres)
10,4,10,25 10=2 times 5 4=2 times 2 10=2 times 5 25=5 times 5 we need to include all of them so we need at leas two 2's, and two 5's 2 times 2 times 5 times 5=100 leact common denomator is 100