\[\boxed{\mathbf{3.}\mathbf{203}}\]
Пояснение.
Решение.
\[\textbf{а)}\ 57a + 43a = (57 + 43) \cdot a =\]
\[= 100a\]
\[a = 321:\]
\[100a = 100 \cdot 321 = 32\ 100.\]
\[a = 998:\]
\[100a = 100 \cdot 998 = 99\ 800.\]
\[\textbf{б)}\ 381p - 181p =\]
\[= (381 - 181) \cdot p = 200p\]
\[p = 59:\]
\[200p = 200 \cdot 59 = 11\ 800.\]
\[p = 623:\]
\[200p = 200 \cdot 623 = 124\ 600.\]