For number 1 which is skew to BC?

Which statement justifies why angle ebc measures 90?

Solve the system of equations using the substitution method. {y=−3x+7x=−2y−16 enter your answers in the boxes.

36x2 + 49y2 = 1,764 the foci are located at: a) (-√13, 0) and (√13,0) b) (0, -√13) and (0,√13) c) (-1, 0) and (1, 0)