Can someone me with similar triangle problems

What number should be added to both sides of the equation to complete this square? x^2-10x=7

Order the measurements from the least to the greatest. 2,720 ml , 24.91 l , 0.0268 kl

Grace is standing 18 feet from a lighthouse and kelly is standing 10 feet from grace. the angle that grace looks up to see the top of the lighthouse is 45°. the angle that kelly looks up to see the top of the lighthouse is y°. find the height, h, of the lighthouse. find the angle, rounded to the nearest tenth of a degree, in which kelly looks up to the top of the lighthouse. to the nearest tenth of a degree, find the value of x° . in two or more sentences, explain your calculations