(3—a)÷{a+2—5÷(a—2)}+2÷(a+3)
=(3-a)÷{(a²-9)/(a-2)}+2/(a+3)
=(3-a)× (a-2)/[(a-3)(a+3)]+2/(a+3)
=-(a-2)/(a+3)+2/(a+3)
=(-a+2+2)/(a+3)
=(4-a)/(a+3)