Simplify (6x2 - 3 + 5x3) - (4x3 - 2x2 - 16

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.

I’m stuck on this equation, anyone got the answer?

5x−4≥12 or 12x+5≤−4 can you with this problem