$a)3\cdot x^4\text{dla x=-3}3\cdot {\left(-3\right)}^4=3\cdot 81=243$

$b){\left(3x\right)}^4\text{dla x=-3}{\left(3\cdot \left(-3\right)\right)}^4={\left(-9\right)}^4=6561$

$c)5\cdot x^3\text{dla x=-3}5\cdot {\left(-3\right)}^3=5\cdot \left(-27\right)=-135$

$d){\left(5x\right)}^3\text{dla x=-3}{\left(5\cdot \left(-3\right)\right)}^3={\left(-15\right)}^3=-3375$