Seriously don’t understand need help asap

Answer:
about 4.3 * 10^14 Hz
(note: Hz = s^-1)
Explanation:
the speed of light = wavelength * frequency
(the speed of light)/wavelength = frequency
(3*10^8 m/s)/(7*10^-7 s) = frequency
4.3*10^14 s^-1 = frequency