To determine which equation is true when \( x = 4 \), we will substitute \( x = 4 \) into each equation and simplify to see if the left-hand side equals the right-hand side.
Let's evaluate each option:
F: \( 3x + 4 = 8 \)
Substituting \( x = 4 \):
\[ 3(4) + 4 = 12 + 4 = 16 \]
Since \( 16 \neq 8 \), this equation is not true.
G: \( 5x - 2 = 18 \)
Substituting \( x = 4 \):
\[ 5(4) - 2 = 20 - 2 = 18 \]
Since \( 18 = 18 \), this equation is true.
H: \( 2x + 8 = 40 \)
Substituting \( x = 4 \):
\[ 2(4) + 8 = 8 + 8 = 16 \]
Since \( 16 \neq 40 \), this equation is not true.
J: \( 4x + 4 = 12 \)
Substituting \( x = 4 \):
\[ 4(4) + 4 = 16 + 4 = 20 \]
Since \( 20 \neq 12 \), this equation is not true.
After evaluating all options, we find that the equation that is true when \( x = 4 \) is:
G: \( 5x - 2 = 18 \)