If you add the negatives first by combining like terms, you'll get...
(-4b + 5) + (-3b + 2) = -7b + 7
Then do...
(-7b + 7) + (7b + 3) = 10
The reason is just 10 is because 7 + 3 = 10 and then the negative 7 and the positive 7 will cancel out and make 0b aka just 0 which leaves you with 10 as your answer.
