Question 726685
(1) r+s=5
(2) 3s+2t=-1
(3) 4r+t=14
..
3s+3r=15 (mult.1st eq by 3)
3s+2t=-1
subtract
3r-2t=16
8r+2t=28 (mult.3rd eq by 2)
add
11r=44
r=4
s=5-r=1
t=14-4r (3rd eq)
=14-16
=-2 
r=4
s=1
t=-2