=( 1/2 fish body+fish tail)+fish tail
= 1/2 fish body +2 fish tail
1/2 fish body = 2 fish tail = 4 * 2 = 8kg.
Fish body = 8 * 2 = 16kg
Fish head = 8+4 = 12kg
Total weight of fish: 16+ 12+4=32 (kg)
Equation: Let the big fish weigh x kilograms, and get the equation according to the meaning of the question:
( 1/2)x + 4 + 4 = x
Solution: x= 16
Weight of big fish: 16+ 16/2+4+4 =32 (kg)