If y varies directly with x and y = 12 when x=11 what is the constant of variation k?

If the speed of an electromagnetic wave is 100,000 cm/s and its wavelength is 100 cm, what is its frequency? a) 100,000 cycles per second (hz) b) 1 × 10-3 cycles per second (hz) c) 10,000,000 cycles per second (hz) d) 1,000 cycles per second (hz)

What are the solutions of the system? solve by graphing. y = -x^2 - 3x + 2 y = -2x + 2

Me : julio wears a blue shirt every 3 days. larry wears a blue shirt every 4 days. on april 11, both julio and larry wore a blue shirt. what is the next date that they will both wear a blue shirt?