$3-6+35:5$

= $-3+7$

= $4$

$-26-\left(-3\right)-\left(-6:\left(-2\right)\right)·\left(-4\right)$

= $-26+3-3·\left(-4\right)$

= $-23+12$

= $-11$

$\left(-9-\left(-12\right)-5\right):\left(-4:\left(-2\right)\right)$

= $\left(-9+12-5\right):2$

= $\left(3-5\right):2$

= $-2:2$

= $-1$

$-5·\left(-8\right)-20+(-7·\left(-5\right)):\left(-7\right)$

= $40-20+35:\left(-7\right)$

= $20-5$

= $15$