How to add 16.9 + 12.1 together

Factor the polynomial 4x4 – 20x2 – 3x2 + 15 by grouping. what is the resulting expression? (4x2 + 3)(x2 – 5) (4x2 – 3)(x2 – 5) (4x2 – 5)(x2 + 3) (4x2 + 5)(x2 – 3)

Adam used 1072.4 gallons of water over the course of 7 days. how much water did adam use, on average, each day?

3x + 4y = 5 x- 3y = -7 solve by substitution