What is equivalent to 3(5+4)

What signals you that factoring by grouping is the best method to use when factoring a problem?

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)

Which statement justifies why angle ebc measures 90?