Hello there!

Explanation:
↓↓↓↓↓↓↓↓↓
First you had to switch sides.

Then you add similar elements.

Divide by 7 from both sides of the equation.

Simplify it should be the correct answer.

Answer⇒⇒⇒⇒⇒t=-2/7
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-Charlie
7/21 can be simplified to 1/3 because 7 divided by 7 equals 7 and 21 divided by 7 equals 3.