In how many years will ₹ 950 produce ₹ 399 as simple interest at 7% ?

Given:

P = ₹ 950

R = 7%

S.I. = ₹ 399

Let time be $t$ years. $\because \text{S.I.} = ₹ \Big(\dfrac{P \times R \times T}{100}\Big)\\[1em] \Rightarrow \text{399} = ₹ \Big(\dfrac{950 \times 7 \times t}{100}\Big)\\[1em] \Rightarrow \text{399} = ₹ \Big(\dfrac{6,650t}{100}\Big)\\[1em] \Rightarrow \text{399} = ₹ \Big(\dfrac{133t}{2}\Big)\\[1em] \Rightarrow t = \dfrac{399 \times 2}{133}\\[1em] \Rightarrow t = \dfrac{798}{133}\\[1em] \Rightarrow t = 6$

Hence, the time is 6 years.