Which test is used for testing the significance of mean

Evaluate:  75 − {18 + (24 ÷ 3)} × 2

5.5 × 3.2 × 2.3 = ?

(880 ÷ 11 + 170) X ? = 40% of 1000 

√(2670+ √(1141+ √(260- √(1251- √(637+ √1521) ) ) ) )  =?

Simplify: 72 ÷ 6 × 3 − 8 + 4

What will come in the place of question mark (?) in the given expression?

(555 + 385 - 535) ÷ 15 X ? = 36 X 30

√225 + 27 × 10 + ? = 320

360 ÷ 9 + 15 % of 200 + ? * 10 = 45 * √25

If √3ⁿ 729, then the value of n is equal to:

If x + y + 3 = 0, then find the value of x³ + y³ – 9xy + 9.