Question

4a + 3 - 9 = -7 + 2 + a

Answer 1

4a + 3 - 9 = -7 + 2 + a
4a - 6 = -5 + a
4a - a = -5 + 6
3a = 1 / : 3
a = 1/3

Answer 2

$4a + 3 - 9 = -7 + 2 + a\\ 4a-6=-5+a\\ 4a-a=-5+6\\ 3a=1\ /:3\\ a=\frac13$