To solve this, we will use the distance formula;
from the question;
RS = 13 x₁=1 y₁=3 x₂=6 y₂=y
substituting into the formula;
Take the square of both-side of the equation
169 = 25 + (y-3)²
subtract 25 from both-side of the equation
144 = (y-3)²
Take the square root of both-side
12 = y-3
add 3 to both-side of the equation
15=y
y=15