a = ?

4a + 12 = 7a - 9

please show workings

1 answer

4a + 12 = 7a - 9

add 9 to both sides

4a + 12 + 9= 7a - 9 + 9
4a + 21 = 7a

subtract 4a from each side

4a + 21 - 4a= 7a - 4a
21 = 3a

divide each side by 3

21/3 = 3a/3
7 = a

or a = 7