Joe went shopping for a guitar in Fairfax. He purchased one originally priced at $240 but discounted 80%. If sales tax in Fairfax is 9.25%, what was the total cost?

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:

48+y= ?

the y is the variable and the ? could also be a variable  

the one where 1 and 2 are directly across from each other.  

see image