We must find the common denominator.
It's LCM of 9 and 6.
Multiples of 6: 0, 6, 12, 18, 24, ...
Multiples of 9: 0, 9, 18, 27, ...
LCM(6, 9) = 18
18 = 3 · 6
18 = 2 · 9
![(4)/(9)=(4\cdot2)/(9\cdot2)=(8)/(18)\\\\(5)/(6)=(5\cdot3)/(6\cdot3)=(15)/(18)\\\\(4)/(9)+(5)/(6)=(8)/(18)+(15)/(18)=(8+15)/(18)=(23)/(18)=(18+5)/(18)=1(5)/(18)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/142289pyvnahw4vv7zxggf61pqcxwtkq69.png)
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Other method:
![(4)/(9)+(5)/(6)=(4\cdot6)/(9\cdot6)+(5\cdot9)/(6\cdot9)=(24)/(54)+(45)/(54)=(24+45)/(54)=(69)/(54)=(54+15)/(54)\\\\=1(15)/(54)=1(15:3)/(54:3)=1(5)/(18)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/mr2oy4ne64mg5jrv4amoaayj31mxglt6uk.png)