begin{linearSystem}
2x&+y&=&2\
x&-3y&=&1
end {linearSystem}

2x +y=2
 x-3y=1

[left{begin{aligned}[c]
2x&+y&=&2\
x&-3y&=&1
end{aligned}right.]

2x+y  =2
 x-3y =1