The algebraic phrase for the sum of three times the opposite of a number and -7 is 3(-x) - 7.
Explanation:
To find this algebraic phrase, we need to use the rules of algebra to express the given statement in mathematical notation. The given statement says that the sum of three times the opposite of a number and -7 is some unknown value.
We can start by expressing the opposite of a number in mathematical notation. The opposite of a number is equal to the number multiplied by -1. So, we can write the opposite of a number as -x.
Next, we can express the fact that the opposite of a number is being multiplied by 3. To do this, we can simply write 3(-x) to represent three times the opposite of a number.
Finally, we can express the fact that -7 is being added to the result. To do this, we can simply write 3(-x) - 7 to represent the sum of three times the opposite of a number and -7.
Therefore, the algebraic phrase for the sum of three times the opposite of a number and -7 is 3(-x) - 7.