Answer:
The value of x - y is 14
Explanation:
∵ x : y = 5 : 3
→ Write it in the form of the fraction
∴ 

→ Multiply both sides by y
∴ 
 × y = 
 × y
∴ x = 
 y ⇒ (1)
∵ x + y = 56 ⇒ (2)
→ Substitute x in (2) by (1)
∴ 
 y + y = 56
→ Add the like terms
∵ 
 y = 56
→ Divide both sides by 

∴ y = 21
→ Substitute the value of y in (1) to find x
∵ x = 
 (21)
∴ x = 35
→ Now find the value of x - y
∵ x - y = 35 - 21
∴ x - y = 14
∴ The value of x - y is 14