d) \( \left(5,6 \times 10^{5}\right)-\left(7,5 \times 10^{6}\right) \)

We start with the expression \[ (5.6 \times 10^5) - (7.5 \times 10^6). \] **Step 1.** Write both numbers with the same power of 10. Since \[ 7.5 \times 10^6 = 7.5 \times 10 \times 10^5 = 75 \times 10^5, \] the expression becomes \[ (5.6 \times 10^5) - (75 \times 10^5). \] **Step 2.** Factor out the common \(10^5\): \[ (5.6 - 75) \times 10^5. \] **Step 3.** Compute the subtraction inside the parentheses: \[ 5.6 - 75 = -69.4. \] Thus, we have \[ -69.4 \times 10^5. \] **Step 4.** Normalize the result to standard scientific notation. Express \(-69.4\) as \(-6.94 \times 10\): \[ -69.4 \times 10^5 = (-6.94 \times 10) \times 10^5 = -6.94 \times (10 \times 10^5) = -6.94 \times 10^6. \] The final answer is \[ -6.94 \times 10^6. \]