To find the total length of the four pieces of wood, we need to add their lengths:

Total length = (4x + 3) + (-12x + 7) + (42x - 9) + (-10x + 5)

Simplifying and combining like terms:

Total length = 24x - 2

Therefore, the total length of the four pieces of wood should be expressed as 24x - 2.

We are given four pieces of wood with lengths (4x + 3), (-12x + 7), (42x - 9), and (-10x + 5). To find the total length of the wood, we need to add the lengths of these four pieces.

Total length of wood = (4x + 3) + (-12x + 7) + (42x - 9) + (-10x + 5)

Simplifying the expression by combining like terms, we get:

Total length of wood = 24x - 4

Therefore, the total length of the four pieces of wood should be 24x - 4.