Answer :
Consider the given expression as,
[tex]\frac{u}{0.9}=\frac{35}{21}[/tex]Multiply both sides by 0.9,
[tex]\begin{gathered} \frac{u}{0.9}\times0.9=\frac{35}{21}\times0.9 \\ u=\frac{5}{3}\times0.9 \\ u=\frac{5}{1}\times0.3 \\ u=1.5 \end{gathered}[/tex]Thus, the value of 'u' is 1.5
Therefore, option C is the correct choice.