Which expression represents a quadratic expression in standard form? * 5x-4
-21-x^2
-15+2x-x^2
x^2-2x-63

Solve for x and y: 217x + 131y = 913; 131x + 217y = 827

The cost of using a service is $0.25 per min. what equation correctly represents the total cost c, in dollars, for d days of use?

Sue's average score for three bowling games was 162. in the second game, sue scored 10 less than in the first game. in the third game, she scored 13 less than in the second game. what was her score in the first game?