Die korrekte Antwort lautet:
21 + 43 = 64

$(22-\left(15+21\right))·20$

= $\left(22-15-21\right)·20$

= $-14·20$

= $-280$

$-2^2-{\left(-3\right)}^3$

= $-4-\left(-27\right)$

= $-4+27$

= $23$