Solve the Decimal Subtraction: 18 - 16.31 in Vertical Format

To avoid confusion in solving the exercise, we will first add two zeros to the number 18 as follows:

$18.00\\-16.31\\$

Now let's solve the exercise in order:

Let's subtract the hundreds after the decimal point:

$0-1=$

Since we cannot solve the exercise, we will borrow ten from the tens digit of the whole number before the decimal point (since the tenths digit after the decimal point is also 0)

Now the tens digit of the whole number before the decimal point will become 7 and the tenths digit after the decimal point will change from 0 to 10

We will borrow ten from the tenths digit after the decimal point and it will change from 10 to 9 and the hundreds digit will change from 0 to 10

Now we can solve the exercise.

Let's subtract the hundreds after the decimal point:

$10-1=9$

Let's subtract the tenths after the decimal point:

$9-3=6$

Finally, let's subtract the whole numbers before the decimal point accordingly:

$8-1-6=1$

$1-1=0$

And we get:

$18.00\\-16.31\\01.69$

We can ignore the zero before the 1 and therefore we get the number: 1.69