Please anser and explain.

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Steve wants to develop a way to find the total cost of any item including sales tax. the sales tax in his city is 6%. his friend jenna writes the expression x + 6x where x is the cost of the item. explain whether her expression is correct based on the situation.

Can someone check if i did this right since i really want to make sure it’s correct. if you do you so much

Acircle has a circumference of 28.36 units what is the diameter of the circle