\(A=3+5+7+-.+97+99\)
\(\Leftrightarrow A=\dfrac{\left(99+3\right).\left[\left(99-3\right):2+1\right]}{2}\)
\(\Leftrightarrow A=\dfrac{102.\left(96:2+1\right)}{2}\)
\(\Leftrightarrow A=\dfrac{102.\left(48+1\right)}{2}\)
\(\Leftrightarrow A=\dfrac{102.49}{2}\)
\(\Leftrightarrow A=\dfrac{4998}{2}\)
\(\Leftrightarrow A=2499\)
