Subtract: (3g -4) - 2(3g + 4)

First, distribute the -2 to both terms inside the parentheses:

3g - 4 - 2(3g) - 2(4)

Simplify:

3g - 4 - 6g - 8

Combine like terms:

(3g - 6g) + (-4 - 8)

-3g - 12

Thus, (3g - 4) - 2(3g + 4) simplifies to -3g - 12.