1. **State the problem:** We need to subtract two numbers in scientific notation: $5.9 \times 10^7$ and $3.4 \times 10^6$, and express the result in standard form. 2. **Recall the rule:** To subtract numbers in scientific notation, they must have the same power of 10. We can rewrite one number to match the other's exponent. 3. **Rewrite the second number:** $3.4 \times 10^6 = 0.34 \times 10^7$ (because $3.4 \times 10^6 = 3.4 \times \frac{10^7}{10} = 0.34 \times 10^7$). 4. **Subtract the coefficients:** $5.9 - 0.34 = 5.56$. 5. **Combine the result:** $5.56 \times 10^7$. 6. **Convert to standard form:** $5.56 \times 10^7 = 55,600,000$. **Final answer:** $55,600,000$