Please any idea on how to solve?

What are “like terms”? why can we only add like terms?

Technicians have installed a center pivot, circular irrigator for a farm that covers 25 acres. a.) how long is the irrigation boom (in feet) from the center pivot to its farthest extent? b.) if the irrigation boom makes 4 full revolutions in a day, how many miles does the end of the boom travel in 5 days?

X^2/100+y^2/25=1 the length of the major axis is: a)5 b)10 c)20