Hi
Golden rule to know by heart : you can only add or substract element of the same kind.
so X^2 with X^2 , X with X , numbers with numbers...
exemple : 2X^2 +3X^2 = 5X^2
but 5X^2 -3X remains that way as 5X^2 is a " X^2" and " 3X" is a " X" so I can't substract two elements of different kind.
Now you have to translate what is ask of you into a calculus.
so : you have
A ) ( 2x^2+4x +5) - ( x^2+3x)
Math is a sport of the mind. You will only progress and become stronger if you train.
So I let you have a shot. beware of signs rules. If you still have trouble, ask in comment section..