Idon’t understand what it is asking so i need with the work

The diver is 23 feet under sea level

Step-by-step explanation:

If we draw a vertical number line (image attached), where point 0 is sea level (the diver's initial position), the first point under sea level is -20, since we are told it dives a distance of 20 ft (the negative sign is only to indicate the direction, since a distance cannot be negative).

Then, the diver goes 10 ft deep. This means now it is 30 ft under sea level and the second point is -30.

After that the diver swims up 12 ft, hence we have to count 12 points up in our number line and the corresponding point is -18.

Finally, the diver swims 5 ft lower and keep that position. Hence, we have to count 5 points below point -18 in the number line, resulting in the last point: -23.

This means the diver's final position is 23 feet under sea level.

If we want to prove it with numbers, we can do it as follows:

20 ft (down)+10 ft (down)-12 ft (up)+5 ft (down)=23 ft

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: