Soal ulangan Matematika

1. x=y-1 and 3x+4y=14
   
2. y=x-5 and 2x+y=5
3. a-8b=20 and 5a-7b=-1
4. 5a+b=10 and 14a+3b=18
5. a+b=-1 and 9a+8b=-7