Answer:
12x^2 + 31x + 20
Explanation:
This type of problem is important all throughout math. Being able to distribute and multiply is very important. I am assuming you mean multiply by the way.
This problem can be re-written as 3x(4x+5) + 4(4x+5)
First distribute the 3x(4x+5)
12x^2 + 15x
Next distribute the 4(4x+5)
16x + 20
Now add both sums
12x^2 + 15x + 16x + 20
Answer
12x^2 + 31x + 20