Please solve this question

What expression is equivalent to 42x-56y

Find the solution of this system of equation -7x+y=-20 9x-3y=36

5. which description does not guarantee that a quadrilateral is a squar ajo is a parallelogram with perpendicular diagonals 0% has all sides congruent and all angles congruent o has all right angles and has all sides congruent 10% is both a rectangle and a rhombus 30%