Solve for k, the constant of variation, in a joint variation problem where y = 520, x = 5, and z = 6.5

What is the equation of the graph below? y=sec(x)-4

Will used 20 colored tiles to make a design in art class. 5/20 of his tiles were red. what is an equivalent fraction for the red tiles?

A33 gram sample of a substance that's used to detect explosives has a k-value of 0.1473. n = noekt no = initial mass (at time t = 0) n = mass at time t k = a positive constant that depends on the substance itself and on the units used to measure time t = time, in days