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.

explanation:

infrared radiation has wavelength in the range between 700 nm and 1 mm. lets' convert these values into scientific notation, keeping in mind that:

let's start from the lower value, we have:

(we moved the dot two places to the left, so we increased the exponent by 2 units, from -9 to -7)

the higher value is:

so, the range of wavelength of infrared radiation is: