(d) 3 years
Let the required time be t years. Then,
72900\(\big(1+\frac{10}{100}\big)^t\) = 133100\(\big(1-\frac{10}{100}\big)^t\)
\(\Rightarrow\) \(\big(\frac{11}{10}\big)^t\)x \(\big(\frac{10}{9}\big)^t\) = \(\big(\frac{11}{9}\big)^3\) \(\Rightarrow\)\(\big(\frac{11}{9}\big)^t\) = \(\big(\frac{11}{9}\big)^3\)
\(\Rightarrow\) t = 3 years.