Inequalities are solved just like equations except that if you
multiply an inequality through by a negative number, you must
reverse the inequality sign. But you won't have to do that with
your inequality:  

Instead of doing yours for you, I'll do one exactly like yours:

 

Multiply through by +4 to clear the fraction.

 

Combine like terms:

 

Add 20t to both sides:



Add 36 to both sides:



Divide both sides by 21:



Now do yours using the same steps.

Yours will also come out an irreducible fraction.

Interval notation



Edwin