If you cannot solve it then answer is here:
Just notice that both side weight is same and total is 24 that makes 12 each side. Again that 12 is divided equally by 6.
Left Side: 3 red diamond = 6 (so each diamond is equal to 2)
2 Green Spade = 6 ( so each spade is equal to 3)
Right Side: 2 Star + 1 Moon = 6
1 diamond + 1 Spade + 1 star = 6 (2 + 3 + 1 star = 6 so star = 1)
So Now 2 Star + Moon= 6 ( 2*1 + Moon = 6 , Moon =4)
Final Answer: Diamond = 2
Spade = 3
Star = 1
Moon = 4