80 is 80% of 100
Let the value we want be x
So, we have it rephrased as 80% of x is 80
Thus, mathematically, we have it that;
[tex]\begin{gathered} \frac{80}{100}\times x\text{ = 80} \\ 80x\text{ = 100}\times80 \\ x\text{ = }\frac{100\times80}{80} \\ x\text{ = 100} \end{gathered}[/tex]