What type of operating system switches tasks based on

Given below an equation having four blanks you have to check from the alternatives which among the given is correct?

21 _ 51 _ 7 _ 12 _ 75

After interchanging the given two signs, what will be the value of the given equation?

X and –

64 + 15 ÷ 90 - 120 X 17

Select the correct combination of mathematical signs that can sequentially replace the “@” sign and balance the following equation.

If the ‘-’ and ‘×’ are interchanged, What will be the value of the following equation?

34 × 22 + 192 ÷ 12 – 8

Which among the given operators should replace the “%” (in the same order) in the given expression below:

5 % 10 % 5 % 36 % 15 % 6

What will be the value of expression if the numbers/digits ‘(30)’ and ‘(13)’ are interchanged?

78 ÷ 30 × 6 + 13 - 14 + 12

Select the correct combination of mathematical signs that can sequentially replace the sign * and make the equation correct.

3 * 12 * 4 * 5 * 4 * 116

Which two signs need to be interchanged to make the following equation correct?

75 – 18 × 80 ÷ 16 + 40 = 125

Select the correct combination of the mathematical signs to replace the ‘@’ symbols in the below equation and thereby balance it: