In this adaptation of the game of Hangman, instead of thinking of a word, you think of an equation.
Write down blanks for each digit and operation symbol.
For example, if you are thinking   2 7 - 1 8 = 9,
write down   _   _   _   _   _   =   _ .
(it is wise to write down your equation on a piece of paper for your own reference.)

The guessers should guess only single digits and operation symbols.
If the guess is a digit or symbol that is used more than once in your equation,
fill in only one of the correct blanks.
A record of incorrect guesses should be kept to avoid their repetition.

The hangman picture can be drawn in different ways.
Perhaps use a rabbit with a head, 2 ears, a body, and 4 legs.

Equations do not have to be limited to one operation symbol.
I use parentheses and multiple operations in my equations.
Here are some examples:
( 3 + 2 ) x 7 = 3 5       So write _ _ _ _ _ _ _ = _ _
4 x ( 7 - 1 ) = 2 4       So write _ _ _ _ _ _ _ = _ _
7 + 9 x - 2 = - 1 1       So write _ _ _ _ _ _ = _ _ _
- 5 - 7 x 2 = - 1 9       So write _ _ _ _ _ _ = _ _ _
- 4 - ( 2 - 3 ) = - 3       So write _ _ _ _ _ _ _ _ = _ _
( - 1 + 5 ) x 6 = 2 4       So write _ _ _ _ _ _ _ _ = _ _