Answer:
Simon has 7 / 10 of the cakes left
Explanation:
by giving 1 / 5 of the cakes away, he is giving 20 % of the cakes away (1/5 = 20%, regardless of the number)
(30 x 0.2 = 6)
and by giving away 10% of the cakes, he has now given away 30 % of the 30 cakes
(30 x 0.3 = 9)
So, he has 70 % of the cakes left
(30 x 0.7 = 21)
So, Simon has 7 / 10 of the cakes left
(70% = 7 / 10)