Which equation combines with the given equation to form a system of equations with the solution x = 3 and y = 9?

a. x + 2y = 21

b.4x + 6y = 64

c.2x + y = 36

d.4x + y = 21

e.-3x + 4y = 33

f.3x + 2y = 28

Find the domain of the function  [tex]f(x) = \sqrt{3x - 7} [/tex]in interval form, the domain of f is what? in advance.

Aregression was run to determine if there is a relationship between hours of tv watched per day (x) and number of situps a person can do (y). the results of the regression were: y=ax+b a=-0.662 b=30.418 r2=0.703921 r=-0.839

If a || b and b | y, then ? a) x || y. b) x | a. c) a | y. d) a || y.