$(4+x) \cdot 3=16$
\(\boxed{x = \frac{4}{3}}\)
Step 1 :\( (4+x) \cdot 3 = 16 \)
Step 2 :\( 3(4+x) = 16 \)
Step 3 :\( 12 + 3x = 16 \)
Step 4 :\( 3x = 4 \)
Step 5 :\(\boxed{x = \frac{4}{3}}\)