Final answer:
The expression is 2t + 2q, where t represents the top and bottom sides and q represents the left and right sides of the envelope.
Step-by-step explanation:
The expression that represents the total number of sides in your envelope using t and q is:
2t + 2q
The term t represents the number of sides along the top and bottom of the envelope, while the term q represents the number of sides along the left and right of the envelope. Multiplying t by 2 gives us the number of top and bottom sides, and multiplying q by 2 gives us the number of left and right sides. Adding them together gives us the total number of sides in the envelope.