Step-by-step explanation:
x+y=3
x=3-y
15 (3-y)+31y =-3
45-y+31y=-3
-y+31y =-3-45
30y÷30=-48÷30
y=-1,6
x+-1,6=3
x-1,6=3
x=3+1,6
x=4,6
