The ratio of the number of chickens in Farm Z to the number of chickens in Farm A was 4 : 7. There were 51 fewer chickens in Farm Z than in Farm A. When 8 chickens escaped from Farm A, the farmer in Farm A bought another 13 chickens. What was the new ratio of the number of chickens in Farm Z to the number of chickens in Farm A in the end? Give your answer in the simplest form.

	Farm Z	Farm A
Before	4 u	7 u
Change 1		- 8
Change 2		+ 13
After	4 u	7 u + 5

Number of fewer chickens in Farm Z than Farm A
= 7 u - 4 u
= 3 u

3 u = 51

1 u = 51 ÷ 3 = 17

Number of chickens in Farm Z
= 4 u
= 17 x 4
= 68

Number of chickens in Farm A
= 7 u
= 17 x 7
= 119

New number of chickens in Farm A
= 7 u + 5
= 119 + 5
= 124

Farm Z : Farm A
68 : 124 _{(÷ 4)}
17 : 31

Answer(s): 17 : 31