Open Middle®
Directions: Using the digits 1 to 9 at most one time each, place a digit in each box to create two equations: one where x has a positive value and one where x has a negative value. You may reuse all the digits for each equation.
Hint
What strategies might you use to find the two values? How do the digits you choose for the constants affect x’s value? Once you’ve found either the positive or negative value for x, how could you find the other?
Answer
There are many answers, but all the positive values will have the constant on the left side have a lesser value than the sum. For example 3x + 5 = 8. All the negative values will have the constant on the left side have a greater value than the sum. For example 3x + 8 = 5.
Source: Robert Kaplinsky in Open Middle Math
8x + 1 = -7
You can only use digits 1-9.
-7 is not an option
Positive:2x+3=5
6x+3=21
x=3