2/81
There is no need to simplify this, it is only a sum. 21 + (10/2) - 18 = 8
Multiply and simplify 3^-2 x3^6
First you do the square root, then the multiplication, then the addition.
few errors in your title: 2 plus 4 = 6 6 plus 9 = 15 10 plus 25 = 35 18 + 81 = 99
81*82/2= 3321
18/81 = 2/9 (divide top and bottom by the hcf of 18 & 81 = 9)
81
(81 ÷ 9) × 2 = 18
4
X= -2
18/81 = 6/27 = 2/9