1. **Calculate the sum and difference of the given numbers:** Given expression: $$(5.8 \times 10^7) + (5.4 \times 10^6) + (1.9 \times 10^6) - (55 \times 10^6) + (5.4 \times 10^6) + (1.9 \times 10^6)$$ First, convert all terms to the same power of 10 for easier addition/subtraction: $5.8 \times 10^7 = 58 \times 10^6$ So the expression becomes: $$58 \times 10^6 + 5.4 \times 10^6 + 1.9 \times 10^6 - 55 \times 10^6 + 5.4 \times 10^6 + 1.9 \times 10^6$$ 2. **Combine like terms:** Sum the positive terms: $$58 + 5.4 + 1.9 + 5.4 + 1.9 = 58 + (5.4 + 1.9 + 5.4 + 1.9) = 58 + 14.6 = 72.6$$ Subtract the negative term: $$72.6 - 55 = 17.6$$ So the result is: $$17.6 \times 10^6 = 1.76 \times 10^7$$ --- 3. **Calculate the average number of people per km$^2$ in England, 2016:** Assuming the total population and area are given or known (not provided in the question), the average density is: $$\text{Average density} = \frac{\text{Total population}}{\text{Area in km}^2}$$ Since no numbers are provided, this step cannot be completed without additional data. --- 4. **Estimate the value of $n$ (number of adults in the club):** Given: - $54$ adults are over 30 years old. - A sample of $20$ adults is chosen, with $8$ over 30. Set up a proportion: $$\frac{8}{20} = \frac{54}{n}$$ Cross-multiply: $$8n = 20 \times 54$$ $$8n = 1080$$ Divide both sides by 8: $$n = \frac{1080}{8} = 135$$ So, the estimated number of adults in the club is $135$. --- **Final answers:** 1. Sum and difference result: $1.76 \times 10^7$ 2. Average density: Cannot calculate without data. 3. Estimated number of adults $n = 135$.