1. **Stating the problem:** We need to find the combined mass of Earth and Venus by performing four operations: addition, subtraction, multiplication, and division. 2. **Given data:** - Mass of Earth $= 5.9 \times 10^{24}$ kg - Mass of Venus $= 4.9 \times 10^{24}$ kg 3. **Formulas and rules:** - Addition: $m_{total} = m_{Earth} + m_{Venus}$ - Subtraction: $m_{diff} = m_{Earth} - m_{Venus}$ - Multiplication: $m_{prod} = m_{Earth} \times m_{Venus}$ - Division: $m_{quot} = \frac{m_{Earth}}{m_{Venus}}$ 4. **Calculations:** **a) Addition:** $$ 5.9 \times 10^{24} + 4.9 \times 10^{24} = (5.9 + 4.9) \times 10^{24} = 10.8 \times 10^{24} = 1.08 \times 10^{25} $$ **b) Subtraction:** $$ 5.9 \times 10^{24} - 4.9 \times 10^{24} = (5.9 - 4.9) \times 10^{24} = 1.0 \times 10^{24} $$ **c) Multiplication:** $$ (5.9 \times 10^{24}) \times (4.9 \times 10^{24}) = (5.9 \times 4.9) \times 10^{24+24} = 28.91 \times 10^{48} = 2.891 \times 10^{49} $$ **d) Division:** $$ \frac{5.9 \times 10^{24}}{4.9 \times 10^{24}} = \frac{5.9}{4.9} \times \frac{10^{24}}{10^{24}} = \frac{5.9}{4.9} \times \cancel{\frac{10^{24}}{10^{24}}} = 1.204 $$ 5. **Final answers:** - a) $1.08 \times 10^{25}$ kg - b) $1.0 \times 10^{24}$ kg - c) $2.891 \times 10^{49}$ kg$^2$ - d) $1.204$ (dimensionless ratio)