1) $(-48) × 72 + 36 × (-304) = (-48) × 2 × 36 + 36 × (-304) = (-96) × 36 + 36 × (-304) = 36 × [(-96) + (-304)] = 36 × (-400) = 36 × 100 × (-4) = 3600 × (-4) = -14 400$
2) $1 - 2 - 3 - 4 + 5 - 6 - 7 - 8 + 9 - 10 - 11 - 12 + ... + 97 - 98 - 99 - 100$
$= (1 - 2 - 3 - 4) + (5 - 6 - 7 - 8) + (9 - 10 - 11 - 11) + ... + (97 - 98 - 99 -100)$
$= (-8) + (-16) + (-24) + ... + (-200)$
$= (-8) × (1 + 2 + 3 + ... + 25)$
$= (-8) × \frac{25 × 26}{2}$
$= (-8) × 325$
$= -2600$
3) $\frac{71 × 52 + 53}{530 × 71 - 180} = \frac{71 × 52 + 53}{53 × 10 × 71 - 18 × 10} = \frac{71 × 52 + 53}{10 × (53 × 71 - 18)} = \frac{71 × 52 + 53}{10 × [71 × (52 + 1) - 18]} = \frac{71 × 52 + 53}{10 × (71 × 52 + 71 - 18)} = \frac{71 × 52 + 53}{10 × (71 × 52 + 53)} = \frac{1}{10}$
