This has been answered by EP.
No it isn't! EP has correctly answered the question you supplied. If you think that answer is incorrect you might well have specified the question incorrectly.
Here it is. If you think its correct, what have you done so far?
EP's result is 720 lights.
1/3 of 720 is 240 so each small tree has 240/12 = 20 lights.
The remainder is 720 - 240 = 480 lights. 3/4 of 480 = 360 lights, so each big tree has 360/10 = 36 lights.
Therefore each big tree has 36 - 20 = 16 more lights than each small tree.