well, to solve this, we gotta get x on one side, alone. What's keeping x from being alone? well, that 18 and 10 are. How do we get rid of them? We can do THAT by moving them to the other side. To move 18 (you typically start with added or subtracted terms if you just want to move stuff over; of course this isn't a rule to swear by, but it works in a lot of cases) you would need to subtract both sides by 18. Remember, we have to do both sides to maintain equaloty, or the same amount of inequality in this case :D
10x + 18 - 18 < -2 - 18
I see that 18-18 is 0, so I succeeded in "getting rid of" it.
10x < -20
Now, 10 and x are being multiplied together, so I have to do the opposite of multiplying to move it. The opposite of multiplication is division.
10x/10 < -20/10
10/10 is 1, so we succeeded in moving it.
x < -20/10
and -20 <10 simplifies to -2
x < -2
Hope that helps!