Answer:
A is x - 4n / 3, B is 6k + 9n, C is 11k + 16n
Explanation:
Pretty simple, you are adding the algebra grids, or substituting variables and making out an equation.
Solving for B: 4k + 6n + 2k + 3n = 6k + 9n
Solving for A: (2k + 3n) + x = 5k + 7n = x - 4n / 3
Solving for C: 6k + 9n + 5k + 7n = 11k + 16n