What two number when multiplied equals -56 but when added equal -1

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15

Jonathan can type 20 documents in 40 minutes ,and susan can type it in 30 minutes and jack can type it in 24 minutes working together ,how much time will it is take them type the same document

Idon't get undoing if its pass adding and subtracting so can someone ? x-2 over 5 = 18