Respuesta :

A common denominator of 7/8 and 1/5 is 40. You times 7/8 by 5/5 which is 35/40. Then you times 1/5 by 8/8 which is 8/40. So 40 is a common denominator of 7/8 and 1/5. 
Hope this helps! :D
abscisa15

gcd(8, 5) =1 ⇒ 8  and 5 are relatively prime ⇒

⇒  a common denominator is 8··5 = 40

[tex]\it \dfrac{^{5)}7}{\ 8} = \dfrac{35}{40} \\\;\\ \\\;\\ \dfrac{^{8)}1}{\ 5} = \dfrac{8}{40}[/tex]