According to given question,
$2a+3b=19$ … (i)
$a–b=2$ … (ii)
$a=2+b$
Now, substituting the value of a in equation (i) we get,
$2(2+b)+3b=19$
$4+2b+3b=19$
$5b=19–4$
$5b=15$
$b=15/5$
$b=3$
So, $a=2+b$
$=2+3$
$=5$
Hence, the value of a is $5$ and b is $3$.