Which of the following statements contain a variable? all that apply a. there are 60 second in a minute b. he is year old c. double the number of pages in the book d. the age of my friend

Which has the greater energy, light of wavelength 519 nm or light with a frequency of 5.42 x 10^8 sec^-1?

Nina has prepared the following two-column proof below. she is given that ∠oln ≅ ∠lno and she is trying to prove that ol ≅ on. triangle oln, where angle oln is congruent to angle lno nina made two errors in the proof. identify and correct the errors.

There are a total of 75 students in the robotics club and science club. the science club has 9 more students than the robotics club. how many students are in the science club?