from clue 3 and 4 -> 1 number can be 7 OR 3 (since 9 is not correct). Now if 7 was correct and placed in proper spot, it conflicts with Clue 1, thus 7 can’t be the correct number and the correct number is 3 and placed at proper spot (which is 3rd spot).

Now from 2nd clue -> two numbers are correct, one is 3 and other one should be 1 (as we know 7 can’t be correct number), since 1 is placed at wrong spot, correct spot for 1 should be first (since 3rd spot is for 3).

Again from Clue 1: 1 number is correct and placed at wrong spot. we are looking for a number at 2nd spot, it should be 5 (as 7 is not in picture and it can’t be 2 since it is placed at 2nd spot), 5 is placed at wrong spot, its correct spot should be 2nd, since we already know 1st and 3rd spot numbers.

Thus the PIN is 153.

Answer: 4
Explanation: Diagonal numbers are multiplication of the bottom number and 3
8*3 = 24
5*3 = 15
x*3 = 12 =? x = 4

Answer: 15
Solution:
If you see there are 3 variables and 3 equations, we can solve the equations and get the variables values and than we can find the value of fourth equation.

From the first equation we can say that ColdDrink = 10
than from the second Burger = (20 – 10)/2 = 5
and from the third equation FrenchFries= (9 – 5)/4 = 1

Thus Burger + FrenchFries * ColdDrink = 5 + 1*10 = 15

here as per BODMAS 5 + 1*10 will be 5 + 10 = 15

-1^n is 1 (if n is even) OR -1 (in n is odd)

but in this equation power is on 1 not -1
-1¹²¹-1¹²² -1¹²³-1¹²^⁴ = -1-1-1-1 = -4