Jawapan

2016-03-14T14:09:49+08:00
5(5+3r)+7 = 0
25 + 15 r + 7 = 0
15r = -32
r = -32/15

less than 127
2016-03-14T14:12:44+08:00
=5(6+3r)+7
=30+15r+7
=37+15r

r=37/15 -it is less than 127