Witch expression is equivalent to 100,000 10/4 10/5 10/6 10/7

How do you use the elimination method for this question? explain, because i really want to understand!

Parallelogram rstu is a rhombus. m∠r = 120° what is m∠t = 120 (what is m∠rsu? )

Two farmers pay a total rent of $140 for a pasture. the first farmer placed $4 oxen in the pasture, and the second farmer placed $30 sheep in the pasture. the farmers split the rent based on the proportion of the pasture eaten by their own animals that month. how much should the first farmer pay, if 1 ox eats as much as 10 sheep in a month?