Which expression is equivalent to is Measure of angle 4?

A triangle has angles 1, 2, 3. The exterior angle to angle 1 is 4, to angle 2 is 5, to angle 3 is 6.
Measure of angle 2 + measure of angle 3
Measure of angle 1 + measure of angle 2
Measure of angle 1 + measure of angle 3
Measure of angle 5 + measure of angle 6

The sum of two numbers is 86, and their difference is 20. find the two numbers

Which expressions are equivalent to k/2 choose 2 answers: a k-2 b 2/k c 1/2k d k/2 e k+k

Awavelength of 610 nm was found to be the most intense wavelength emitted by copper. answer the following questions about this wavelength of light. a) what is this wavelength in cm? b) what is the frequency that corresponds to this wavelength? c) what is the energy of light of this wavelength? d) what is the wavenumber corresponding to this wavelength?