Which soil process leads to the formation of a hardpan

What value should come in place of (?) in the given expression.

{(36)² − (28)²} ÷ 8 + 9² = ?

Simplify: 48 ÷ 4 × 2 + 5 × (7 − 3)

?% of 18% of 2600 = 234

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

(12.09)² × 5.98 ÷ 26.95 = ? + 25 

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

(555 + 385 - 535) ÷ 15 X ? = 36 X 30

(11/12) × (18/22) × (4/3) + 3 = ?²

The value of (43-3× (4×6+12/6 ×6-4×5) +4)?

(392 + 427 + 226 – 325) ÷ (441 + 128 – 425) = ? 

The value of [(3√2+2) × (3√2-2)] of 13 + 15 is:

`2(1/3)` + `4(1/4)` + `4(2/3)` + `8(7/6)` + ? = `4(3/5)xx4(1/2)`