Question 161336
(7X^3 + 3X^2 + 5X) - (3X^3 + X)

Use the distributive porperty

7x^3 +3x^2+5x-3x^3-x

Combine like terms 

(7-3)x^3+3x^2+(5-1)x

Simplify

4x^3+3x^2+4x