Step-by-step explanation:
Let x be the pound.
The ratio is 5:7
Then,
The 1st pound be 5x
and
2nd pound be 7x
5x + 7x = £1200
12x = £1200
x = £1200/12
x = £100
The 1st pound be
5x = 5×£100 = £500
And
2nd pound be
7x = 7×£100 = £700