Mathew travelled a distance of 61 miles in 9 hours. He travelled partly on foot at 4 miles/hr and partly by bicycle at 9 miles/hr. What is the distance travelled on foot ?

Question

$\begin{array}{1 1} (a)\;15 \;miles \\(b)\; 16 \;miles \\(c)\; 10\; miles \\(d)\; 20\; miles \end{array}$