Step 1
Write out all values
Old value = 640
New value = 480
[tex]\begin{gathered} \text{Percentage decrease = }\frac{Old\text{ value - New value}}{\text{old value}}\text{ x 100} \\ \text{ = }\frac{640\text{ - 480}}{640\text{ }}\text{ x 100\%} \\ \text{ = }\frac{160}{640}\text{ x 100\%} \\ \text{ = }\frac{160\text{ x 100}}{640} \\ \text{ = }\frac{16000}{640} \\ =\text{ 25\%} \end{gathered}[/tex]You
