If ' - ' stands for ' ÷ ' , ' + ' stands for ' x ' , ' ÷ ' stands for ' - ' and ' x ' stands for ' + ' , find out which one is correct .

Try all option one by one;
From option ( b )
49 - 7 + 3 ÷ 5 x 8 = 24
Change the sign, as per the question,
49 ÷ 7 x 3 - 5 + 8 = 24
Apply the BODMAS rule
B - Brackets first
O - Orders (i.e. Powers and Square Roots, etc.)
DM - Division and Multiplication (left-to-right)
AS - Addition and Subtraction (left-to-right)
Now Applying the BODMAS rule one by one.
49 ÷ 7 x 3 - 5 + 8 = 24
After Division
7 x 3 - 5 + 8 = 24
After Multiplication
21 - 5 + 8 = 24
After Addition
29 - 5 = 24
After subtraction
24 = 24