Explicação passo a passo:

B)

[tex]3\left(-6\right)+\left(-5\right)\left(-7\right)\\-18+\left(-5\right)\left(-7\right)\\-18+35\\17[/tex]

C)

[tex]\left(-7\right)+\left(-8\right)\div \left(-2\right)\\\left(-7\right)+4\\-3[/tex]