A two-digit number has the property that the units digit

is 4 less than the tens digit and the tens digit is twice the
units digit. What is the number?

The possible tens digits are in the first column; the possible ones digits are in the second column.

9 - 5
8 - 4
7 - 3
6 - 2
5 - 4
4 - 0

Which set of digits meets the other criterion?

84

To find the two-digit number that meets the given conditions, we can use algebraic reasoning. Let's assign variables to the digits of the number to make it easier to solve:

Let the tens digit be represented by the variable "x."
Let the units digit be represented by the variable "y."

According to the given conditions, the units digit is 4 less than the tens digit, which can be written as:
y = x - 4

The other condition states that the tens digit is twice the units digit:
x = 2y

Now we have a system of equations that we can solve simultaneously to find the values of "x" and "y." Substituting the second equation into the first, we get:
y = 2y - 4
4 = y

Substituting this value of "y" into the second equation, we find:
x = 2(4)
x = 8

So, the tens digit is 8, and the units digit is 4. Therefore, the number is 84.