How do i solve with pethagoem theoem 3d

7x+8y=-18, 4x-9y=-3 solve the system of equations

The last time i bought this product , it cost $20.00 but it looks like it cost 29. 60 today? what is the increase

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