Formulas:

=(D4*E4)*21%

=SI(C5="Sandalia";(D5*E5)*10%;0)

=D4*E4+F4-G4

=CONTAR.SI(A4:A20;"Ana")

=CONTAR(E4:E20)

=CONTARA(E4:E20)

=SUMAR.SI(C4:C20;"Zapato";D4:D20)