So I had a 3d shapes test today in geometry. I did everything according to the notes, but my grade was a C+ I'm still confused why it's wrong someone pls help me!

When using the linear combination metho e linear combination method to solve a system of linear equations, the four options are:

Aplane is taking off from bangladesh headed to new york city. at the same time, a plane from new york city is headed to bangladesh is also taking off. the plane bound to new york city is traveling at 600 mph, while the plane traveling to bangladesh is traveling at 400 mph. how far from new york city will the two planes meet if the distance between new york city and bangladesh is 8,000 miles?

The base of a triangle exceeds the height by 9 inches. if the area is 180 square inches, find the length of the base and the height of the triangle.