In this case, we'll have to carry out several steps to find the solution.
Step 01:
Data
4a + 21 > 10a - 9
a ==> ?
Step 02:
Inequality
4a + 21 > 10a - 9
4a + 21 - 10a > 10a - 9 - 10a
-6a +21 - 21 > -9 - 21
-6a / - 6 > - 30 / - 6
a < 5
The answer is:
a < 5
