Answer:
£1920
Explanation:
The amount she spent in 2016 is 20% less than 2017. 20% less than is the same as 80% of the amount she spent in 2017. So, to find how much she spent in 2016, multiply 2400 by 0.80 (the decimal form of 80%):
2400 * 0.8 = 1920
Emily spent £1920 on holiday in 2016.
I hope this helps :)