Your answer is 28x^2-37x+12
1) Use the FOIL method: (a+b)(c+d)=ac+ad+bc+bd
28x^2-21x-16x+12
2) Collect like terms
28x^2+(-21-16x)+12
3) Simplify
28x^2-37x+12
Use FOIL
28x-21x-16x+12
-9x+12