Combine like terms to create an equivalent expression. -3.6-1.9t+1.2+5.1t

Ijust need these 2 questions answered (the second pic is just confirmation i'm not confident in that answer)

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

Find the vertex for the parabola given by the function ƒ(x) = −3x2 − 6x.