How do I do b) in the attached file?

≈ 81.6 m

Step-by-step explanation:

The model of the situation is a right triangle

let h be the height of the cliff

Using the tangent ratio in the right triangle

tan58° = = ( multiply both sides by 50 )

50 × tan58° = h

We have to add on the height her eye was above ground , then

h = 50 × tan58° + 1.6 ≈ 81.6 m ( to 1 dec. place )

Here you are. 
Everything explained step by step.

if you put this fractions to a common denominator, everything become clear. 7/12 = 35/60; 1/2 = 30/60; 2/5 = 24/60; 2/3 = 40/60. So WHICH one is the bigger? CLEARLY 40/60 - that means: 2/3