Can someone please explain to me how to get the answer for the question is the picture? I don't get it at all, and the internet isn't helping. Please explain the way you got the answer

The original price of the item is $28.

Step-by-step explanation:

So to find the original price, we have to divide the sale price by the result of one minus the discount in percentage form.

So:

First convert 25% to a decimal, 0.25.

OP(original price) = 21 ÷ 1 - 0.25 =

1 - 0.25 = 0.75

21 ÷ 0.75 = 28.

13875138answer:

step-by-step explanation:

use a calculator!

the value of v.w= -12.

step-by-step explanation:

we are given three vector r,v and w as:

r = < 5, -5, -2> ; v = < 2, -8, -8> ; w = < -2, 6, -5>

we know that r,v and w could also be represented as:

r=5i-5j-2k

v=2i-8j-8k

and w= -2i+6j-5k

where i,j and k are the unit vectors of x,y and z-axis respectively.

also we know that it has the following property:

i.i=1 ; j.j=1; k.k=1

and i.=j.i=i.k=k.i=j.k=k.j=0

i.e. when we multiply two vectors or we find it's dot product we need to only multiply the components of x coordinates with each other; y with each other and z with each other.

hence, v.w= (2i-8j- -2i+6j-5k)

                  = 2×(-2)+(-8)×(6)+(-8)×(-5)

                  = -4-48+40

                  = -12

hence, v.w= -12