Use a common denominator to write an equivelent fractions for each fraction.
1. 5/12,2/9 common denominator=

Sorry for not giving you the calculation here -

5/12 and 2/9 have denominators divisible by only 3 right? Well The common denominator that can then change is 3 because that's the only number they have in common (except 1) 

45 is the only number in both sets