We ask what fraction of 100% is 2.2%. To find out we work out: 100/2.2=500/11=45.4545 approx.
Since 100% is 45.4545 bigger than 2.2% we can work out 25 billion times 45.4545 to give us the much larger number of phones: 25 billion * 45.4545=12500/11 billion = 1136 billion phones (approx).