If these equations are correct, -7+5b=1, 5b=8, b=8/5=1.6.
6a=31+7b=31+11.2=42.2, a=42.2/6=211/30 or 7.033 approx.
If the equations should be: 6a-7b=31, -7a+5b=1,
then:
30a-35b=155
-49a+35b=7
Add these: -19a=162, a=-162/19.
5b=1+7a=1-1134/19=-1115/19, b=-223/19.