Write an expression that represents 6 less than a number times 5

Determine which expressions represent real numbers and which expressions represent complex number. asaaap! plis!

You give a $4 tip for a meal that cost $22. approximately what percent of the bill was your tip?

How many different three-digit numbers can be formed using the digits 1 comma 2 comma 9 comma 6 comma 4 comma 3 comma and 8 without repetition? for example, 664 is not allowed.