13-{8x15-[(7x5+5)÷8+20÷(28÷4-3)]}÷11
13-{8x15-[(7x5+5)÷8+20÷(28÷4-3)]}÷11
13-{8x15-[(7x5+5)÷8+20÷(28÷4-3)]}÷11
$13-{8×15-[(35+5)÷8+20÷(7-3)]}÷11$
$13-{120-[40÷8+20÷4]}÷11$
$13-{120-(5+5)}÷11$
$13-{120-10}÷11$
$13-110÷11$
$13-10=3$
$13-\{8×15-[(7×5+5) ÷ 8+20÷(28÷4-3)]\}÷11$ =
= $13-\{120-[(35+5) ÷ 8+20÷(7-3)]\}÷11$ =
= $13-\{120-[40 ÷ 8+20÷4]\}÷11$ =
= $13-\{120-[5+5]\}÷11$ =
= $13-\{120-10\}÷11$ =
= $13-110÷11$ =
= $13-10$ =
= $3$