Let the larger number = y and the smaller number = x.
The largest number is 10 less than twice the smaller number. Remember that less than means subtract the 10 from the other amount while twice means multiply by two. Therefore,
y = 2x - 10
The sum of the two numbers is 38. Remember sum means add the two numbers to get their result. Therefore,
x + y = 38
Since y = 2x - 10, we rewrite the lower equation as:
x + (2x - 10) = 38
Solving:
3x - 10 = 38
3x = 48
x = 16
The lesser number is 16 and the greater number is 2(16) - 10 or 22.
A decrease of 8.25% means the reduction factor is 100-8.25=91.75%=0.9175. The shrinkage over 15 years is 0.9175¹⁵=0.27485 approx, so the size of the forest will be 3100×0.27485=852 sq km approx.
