WILL MARK AS BRAINLIST PLZ HELP ASAP AND SHOW ALL WORK!!!

If the graphs of the linear equations in a system are parallel, what does that mean about the possible solution(s) of the system? a. there are infinitely many solutions. b. there is no solution. c. there is exactly one solution. d. the lines in a system cannot be parallel.

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

Which statement justifies why angle ebc measures 90?