To solve for x, you need to isolate/get the variable "x" by itself in the equation:
16x - 3(4x + 5) = 2x + 9 Distribute -3 into (4x + 5)
16x + (-3)4x + (-3)5 = 2x + 9
16x - 12x - 15 = 2x + 9 Combine like terms (terms that have the same variable and power/exponent), which are 16x - 12x, as they have the same variable "x" and a power/exponent of 1.
4x - 15 = 2x + 9 Subtract 2x on both sides
4x - 2x - 15 = 2x - 2x + 9
2x - 15 = 9 Add 15 on both sides
2x - 15 + 15 = 9 + 15
2x = 24 Divide 2 on both sides to get "x" by itself
x = 12