Step-by-step explanation:
[tex]\dfrac{a}{b} = \dfrac{c}{d}[/tex]
Add 1 to both sides of the equation:
[tex]\dfrac{a}{b} + 1 = \dfrac{c}{d} + 1[/tex]
Note that
[tex]\dfrac{a}{b} + 1 = \dfrac{a + b}{b}[/tex]
Likewise,
[tex]\dfrac{c}{d} + 1 = \dfrac{c + d}{d}[/tex]
Therefore,
[tex]\dfrac{a + b}{b} = \dfrac{c + d}{d}[/tex]
