If w/9 = 0.9
w = ?

w/9 is a fraction :D

w= 8,1

Step by step:

w/9= 0.9

the 9, instead of dividing in becomes a multiplication, which you will multiply with 0.9, which is the answer

which goes like...

w/9 = 0.9  

w = 0.9 x 9 = 8,1

And then we check it if it's true

8,1 / 9 = 0.9

And it is

is correct

w= 8.1

the largest number of the four options is 1.8 x 10-2

you have it in scientific notation.

1.80 x 10-6   = 0.00000180

1.80 x 10-4   = 0.000180 (bigger, or "less small", than the former one)

so

1.8 x 10-2       = 0.0180. as you see. the "less small", or the biggest one of them all.

as you have negative exponent, it means you are dividing 1.8 by 100 (i.e. moving the dot towards left, two times).

if you had positive exponent for the scientific notation, power of tenths, you would be multiplying times 100 (moving the dot towards right) as below:

1.8 x (10)2 = 180

so. if you have negative exponent in scientific notation, move the dot toward left. if it is positive, toward right as many times the exponent tells you.