Calcolare il valore delle seguenti espressioni:

Esercizio 1 \[ 5\times\left(-7\times2\right)+3-8= \] \[ 5\times\left(-14\right)+3-8= \] \[ -70+3-8=-75 \] Esercizio 2 \[ -2-3\times\left[-4\times\left(-5+1+4\right)+3\times8\times\left(-2\right)\right]\times\left(7-4-2-1\right)= \] \[ -2-3\times\left[-4\times0+3\times8\times\left(-2\right)\right]\times0= \] \[ -2-3\times\left[0-48\right]\times0= \] \[ -2-0=-2 \] Esercizio 3 \[ \left\{ -3\times\left[\left(-2-4\right)+2\times\left(-4\right)\right]\div\left(-7\right)\right\} +\left[2\times\left(5+1\right)+\left(-6\right)\div\left(-3\right)\right]= \] \[ \left\{ -3\times\left[\left(-6\right)+2\times\left(-4\right)\right]\div\left(-7\right)\right\} +\left[2\times\left(6\right)+\left(-6\right)\div\left(-3\right)\right]= \] \[ \left\{ -3\times\left[\left(-6\right)+\left(-8\right)\right]\div\left(-7\right)\right\} +\left[12+2\right]= \] \[ \left\{ -3\times\left[-14\right]\div\left(-7\right)\right\} +14= \] \[ -6+14=8 \] Esercizio 4 \[ \left\{ 5\times\left[\left(-3+5\right)+\left(2-8\right)+2\times4\right]\div\left(-5\right)\right\} -20= \] \[ \left\{ 5\times\left[2-6+2\times4\right]\div\left(-5\right)\right\} -20= \] \[ \left\{ 5\times\left[2-6+8\right]\div\left(-5\right)\right\} -20= \] \[ \left\{ 5\times4\div\left(-5\right)\right\} -20= \] \[ \left\{ 20\div\left(-5\right)\right\} -20= \] \[ -4-20=-24 \]