, 2021

Solution 1

We undo each of the operations in reverse order.

The final result, 85, was obtained by multiplying a number by 5. This number was $85 \div 5 = 17$.

The number 17 was obtained by decreasing $n$ by 2. Thus, $n = 17 + 2 = 19$.

Solution 2

When $n$ is decreased by 2, we obtain $n-2$.

When $n-2$ is multiplied by 5, we obtain $5 \times (n-2)$.

From the given information, $5 \times (n-2) = 85$ which means that $5n - 10 = 85$.

From this, we obtain $5n = 95$ and so $n = \dfrac{95}{5} = 19$.