We have the dominators: 5, and 3.
We must find the LCM (Least Common Multiple) of 5 and 3:
The multiples of 5: 0, 5, 10, 15, 20, 25, ...
The multiples of 3: 0, 3, 6, 9, 12, 15, 18, ...
LCM(5, 3) = 15
[tex]\dfrac{7}{5}=\dfrac{7\cdot3}{5\cdot3}=\dfrac{21}{15}=1\dfrac{6}{15}\\\\\dfrac{7}{3}=\dfrac{7\cdot5}{3\cdot5}=\dfrac{35}{15}=2\dfrac{5}{15}[/tex]
We accept 15 as a unit.
Look at the picture.
