Can you tell me how they got this answer

Question

The problem is write the resulting polynomial in descending order of degree (5y+4)+(3y+1). Its saying the answer is 10y+12. I solved it the same way I solved the problem before (which my answer was correct) but my answer for  problem was 8y+5

Answer 1

The way this problem is written the answer is 8y+5

 

 (5y+4)+(3y+1)

 

= 5y + 3y + 4 + 1

 

= 8y + 5

 

Even if these were meant to be multiplied as in

 (5y+4)(3y+1)

it would still not equal to

10y + 12

 

Your book is incorrect.  Typing mistakes such as this do occur.