We have in a) that
[tex]\begin{gathered} 70\cdot\text{ }\frac{4}{100}\text{ = }\frac{\text{70 }\cdot\text{ 4}}{100} \\ =\text{ 2.8} \end{gathered}[/tex]So the answer for a) is 2.8
Now in b) we have that
[tex]5\cdot\text{ }\frac{100}{20}\text{ = 25}[/tex]So the answer for b) is 25%.