The sum of a number and five is twelve.

The equation that can be used to represent the given expression is x + 5 = 12 and the unknown number, x is 7

let

the unknown number = x

x + 5

x + 5 = 12

solve for x

x + 5 = 12

x = 12 - 5

x = 7

Therefore, the value of the unknown number, x is 7

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"a number" = 7

Step-by-step explanation:

let "a number" = x.

x + 5 = 12

Isolate the variable x. Note the equal sign, what you do to one side, you do to  the other. Subtract 5 from both sides.

x + 5 (-5) = 12 (-5)

x = 12 - 5

x = 7

7 is your answer.

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8

step-by-step explanation:

this is a subtraction problem.

10 - 2 = 8