To evaluate the expression 24 / (a + b) when a = 6 and b = 12, first substitute the values of a and b into the expression:
24 / (6 + 12)
Next, simplify the expression according to the order of operations (parentheses first, then division and addition):
24 / 18
Divide 24 by 18:
24 / 18 = 1.33333333333
Therefore, 24 / (a + b) = 1.33333333333 when a = 6 and b = 12.