To make the given equation correct, we need to interchange two signs. Let's analyze the equation step by step to determine which signs should be interchanged.

Step 1: Simplify the expression on the left side of the equation.
42 × 7 ÷ 8 = 294 ÷ 8 = 36.75 (rounded to two decimal places)

Step 2: Simplify the expression on the right side of the equation.
12 - 24 = -12

Step 3: Compare the results of both sides of the equation.
36 is not equal to -12.

Since the equation is not currently correct, we need to interchange two signs to make it correct. Let's consider the possible options:

a) and –
This option suggests interchanging the plus sign (+) with the minus sign (-). However, interchanging these signs would not result in a correct equation because the simplified expressions on both sides will still be different.

b)× and –
This option suggests interchanging the multiplication sign (×) with the minus sign (-). Again, interchanging these signs would not result in a correct equation as the simplified expressions on both sides would still be different.

d) and ÷
This option suggests interchanging the plus sign (+) with the division sign (÷). However, interchanging these signs would not result in a correct equation as the simplified expressions on both sides would still be different.

c)× and ÷
This option suggests interchanging the multiplication sign (×) with the division sign (÷). Let's see if this interchange results in a correct equation.

42 ÷ 7 × 8 - 12 ÷ 24 = 36

Step 1: Simplify the expression on the left side of the equation.
42 ÷ 7 × 8 = 6 × 8 = 48

Step 2: Simplify the expression on the right side of the equation.
12 ÷ 24 = 0.5

Step 3: Compare the results of both sides of the equation.
48 - 0.5 = 47.5

Since 47.5 is not equal to 36, this option does not result in a correct equation.

Therefore, the correct option is c)× and ÷.