Final answer:
By setting up a system of linear equations from the problem and either subtracting or substituting, we find that the price of a citron is 3 units and the price of a wood apple is 8 units, which corresponds to option a).
Step-by-step explanation:
To find the price of a citron and the price of a wood apple, we can set up a system of linear equations based on the information given:
- For the first situation, the equation would be 8C + 3W = 48, where C is the price of a citron and W is the price of a wood apple.
 - For the second situation, the equation would be 3C + 8W = 73.
 
Now we will solve this system using the method of substitution or elimination to find the values of C and W.
Using Substitution or Elimination
Multiply the first equation by 3 and the second equation by 8 to make the coefficients of C equal:
- 24C + 9W = 144 (first equation multiplied by 3)
 - 24C + 64W = 584 (second equation multiplied by 8)
 
Subtract the first new equation from the second new equation to eliminate C:
- 55W = 440 (subtracting the equations)
 
Divide by 55 to find the price of a wood apple:
Substitute W = 8 back into the first original equation:
- 8C + 3(8) = 48
 - 8C + 24 = 48
 - 8C = 24
 - C = 24 / 8
 - C = 3 units
 
Therefore, the price of a citron is 3 units and the price of a wood apple is 8 units.