a, $\dfrac{5x}{x+5}$ + $\dfrac{10}{x+5}$ 

= $\dfrac{5x + 10}{x + 5}$

b, $\dfrac{4x}{2x+3}$ + $\dfrac{6}{2x+3}$

= $\dfrac{4x+6}{2x+3}$

= $\dfrac{2(2x+3)}{2x+3}$

$\text{= 2}$

c, $\dfrac{9x}{x+3}$ + $\dfrac{27}{x+3}$

= $\dfrac{9x+27}{x+3}$

= $\dfrac{9 ( x + 3 ) }{x+3}$

$\text{= 9}$

d, $\dfrac{20}{x +10}$ + $\dfrac{2x}{x +10}$

= $\dfrac{20 + 2x}{x + 10}$

= $\dfrac{2 (  10 + x ) }{x+10}$

$\text{= 2 }$

e, $\dfrac{1}{x + 4}$ + $\dfrac{3}{x - 2}$

 = $\dfrac{ x - 2 + 3 ( x + 4 ) }{ ( x + 4 )( x - 2 ) }$

 = $\dfrac{ 4x + 10 }{( x + 4 )( x - 2 )}$

f, $\dfrac{3}{x + 2}$ + $\dfrac{4}{x - 5}$

 = $\dfrac{ 3x - 15 + 4x + 8}{( x + 2 )( x - 5 )}$

 = $\dfrac{ 7x - 7 }{ ( x + 2 )( x - 5 )}$

g, $\dfrac{2}{x + 6}$ + $\dfrac{1}{x - 4}$

 = $\dfrac{ 2x - 8 + x + 6 }{ ( x + 6 )( x - 4 )}$

 = $\dfrac{ 3x - 2 }{ ( x + 6 )( x - 4 ) }$

h, $\dfrac{8}{x + 3}$ + $\dfrac{6}{x - 2}$

= $\dfrac{8x -16 + 6x + 18}{ ( x + 3 )( x - 2 )}$

= $\dfrac{14x + 2 }{( x + 3 )( x - 2 )}$