The number of equation questions in the exercise book of the first volume of the fifth grade mathematics is expressed by letters (1).

There are three consecutive natural numbers in (1). If the middle number is n, how can the other two natural numbers be expressed by formulas?

(2) Say the meaning of the formula of the following letters.

①8x means (eight x's are added) and also means (I don't know).

② The square of x (the symbol 2 representing the square in the upper right corner can't be typed,) means (x times x).

(3) 2x+4 means (2 x's are added, plus 4).

(3) first judge right and wrong, and then correct.

1. 18 The number less than x is 18+3x. ( × )

Correction: 3x- 18

Second, omitting the multiplication sign, x×6-x×2 can be written as 6x square -x square. ( × )

Correction: x squared times 6-2x.

3.3x-6 = 3 (x-6) (x)

4.5a+5b-3c=5(a+b)-3c( √)

Correction: