Help me with this please!

How do astronomers measure the amount of dark matter in the universe

Which of these statements properly demonstrates the angle addition postulate for the m∠afc m∠afc ? a. m∠afc=m∠afb+m∠bfd m∠afc=m∠afb+m∠bfd b. m∠afc=m∠afb+m∠bfc m∠afc=m∠afb+m∠bfc c. m∠afc=m∠cfd+m∠dfe m∠afc=m∠cfd+m∠dfe d. m∠afc=m∠afb+m∠dfc+m∠cfb m∠afc=m∠afb+m∠dfc+m∠cfb

Mars has a surface gravity that is only 0.38 (a little over one-third) that of earth's. thus, the weight of an object will also be 0.38 times that of earth. what is the g. p.e. of a climber who weighs 675 newtons on earth at the top of 26,000-meter olympus mons?