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
a = ?
4a + 12 = 7a - 9
please show workings
1 answer