Answer: The correct option is fourth, i.e.,
.
Step-by-step explanation:
It is given that,

By the rule of of congruence SSS.
Since both triangles are congruent, it means the ratio of their corresponding sides are equal.
The sides of first triangle are RS, ST, RT and their corresponding sides are RY, YX and RX respectively.
So,

Where, k is any constant.
Since it is given that,

and we know that
is also equal to these ratios, therefore, the fourth option is correct.