If 'x' stands for '+', '<' for '-', '+' for ' ÷', '>' for 'x', '-' for '=', ' ÷' for '>' and '=' for '<', then state which of the following is true?

6 * 4 * 12 * 12
From option (d),
6 x 4 - 12 = 12
? 12 = 12

From option (b),
49 - 7 + 3 ÷ 5 x 8 = 24
Change the sign, as per the question,
49 ÷ 7 x 3 - 5 + 8 = 24
? 7 x 3 - 5 + 8 = 24
? 21 - 5 + 8 = 24
? 24 = 24

16 x 2 ÷ 25 + 7 - 4
= 16 ÷ 2 + 25 - 7 x 4
= 8 + 25 - 28
= 25 - 20 = 5

Rules
(i) (2-digit even number) ÷ ( Even number)
(ii) (Even number) x (Prime number)
(iii) (Odd number) + (Odd number)
(iv) (3-digit number) - (2-digit perfect square number)
(v) (3-digit number) ÷ (2-digit non-perfect square number)
Solution
1st Row 84   14   13 ? 84 ÷ 14 = 6       [rule (i)]
?     6 x 13 = 78     [rule (ii)]
2nd Row 360   24   17 ? 360 ÷ 24 = 15     [rule (v)]
?         15 + 17 = 32     [rule (iii)]
? Resultant difference = 78 - 32 = 46

Rules
(i) (Odd number) x (Composite odd number)
(ii) (Even number) + (Odd number)
(iii) (Even number) ? (Perfect square number), then (Perfect square number) - (Even number)
(iv) (Odd number) ÷ (Prime odd number)
(v) (Odd number) - (Even number)
Solution
1st Row 14   5   9 ? 14 + 5 = 19       [rule (ii)]
?     19 x 9 = 171     [rule (i)]
        = w
2nd Row 24   w   88 ? 24   171   88
?         24 + 171 = 195   [rule (ii)]
?       195 - 88 = 107     [rule (v)]
? Resultant of second row = 107

Change the proper sign according to question and try all option one by one by applying the BODMAS Rule.
'-' ? ÷
'+' ? '-'
÷ ? 'x'
'x' ? '+'
? 70 ÷ 2 - 4 x 5 + 6 = 21
? 35 - 20 + 6 = 21
? 15 + 6 = 21
? 21 = 21

Using the proper symbols, we have
24 ÷ 12 - 8 + 9
Now Apply the BODMAS Rule,
= 24 x 12 + 18 ÷ 9
= 288 + 2 = 290

Using the correct symbols, we have
1 8 R 9 P 2 Q 8
= 18 ÷ 9 + 2 x 8
= 2 + 2 x 8 = 2 + 16 = 18

If we interchange 'x' and '-' , the equation changes into
3 x 9 - 27 + 9 ÷ 3 = 27 - 27 + 3 = 3

If we interchanges signs '÷' and 'x', then the equation changes into
4 ÷ 2 + 6 x 2 - 12 = 2 + 12 - 12 - 2