To solve the equation \( 0.5x + 4.2 = 5.9 \), we first isolate \( x \) by following these steps:
- Subtract 4.2 from both sides:
\[ 0.5x = 5.9 - 4.2 \]
Calculating the right side:
\[ 5.9 - 4.2 = 1.7 \]
So, we have:
\[ 0.5x = 1.7 \]
- Next, divide both sides by 0.5 to solve for \( x \):
\[ x = \frac{1.7}{0.5} = 3.4 \]
Thus, the solution to the equation \( 0.5x + 4.2 = 5.9 \) is:
\[ \boxed{3.4} \]