3x - 5 = 55 (Simplifying Like terms by adding and subtracting)
3x = 55+5 ( Move -5 towards Right hand side of equal as there is 55 which is like term of -5 and if we move any number or value from one side of equal towards other the sign of that value would change)
3x = 60
X= 60/3 ( Move 3 toward others side as there is like term of 3 which is 60 but as on Left hand side of equal sign 3 is multiplying with "X" so when we move any number or value toward other side the operation or sign of that value or number would be change, Multiply change into Divide and vice versa and Add change into subtraction and vice versa)
when solving sales tax it's pretty simple because all you do is add everything for a subtotal and multiply your sub total by the tax so i'll use the first as an example your subtotal is 19.96 x0.05 to get 0.99 <-- your sales tax and your final total with tax to be 20.96
