Answer
$-3a+3$
Work Step by Step
We write an expression to express this addition problem: $3a^2+4a-7+(-3a^2-7a+10)$
We use the commutative and associative properties of addition to group like terms: $(3a^2+(-3a^2))+(4a+(-7a))+(-7+10)$
We combine the like terms: $0-3a+3=-3a+3$