10. When Raphael solved the system below by using the method of elimination, he changed the second equation to -8x - 2y =-2. What property justifies this manipulation?
8x + 3y = 7
4x + y =1

Having a hard time understanding this question (see attachment).

Look at the figure below: triangle abc is a right triangle with angle abc equal to 90 degrees. the length of ac is 5 units and the length of ab is 4 units. d is a point above c. triangle adc is a right triangle with angle dac equal to 90 degrees and dc parallel to ab. what is the length, in units, of segment cd?

Zack and tia played chess for 50 min they put the chessboard away at 11: 20 when did they start