Let the unknown endpoint be (x₂ , y₂) and the known (x₁ , y₁)
mid-point =

= (A , B)
plug in the known values
=>
separate the two parts of the equation for the formula and solve
for the value of the unknown y and x
=> A :

-3 + x₂ = (5)(2)
x₂ = 10 + 3
= 13
B:

5 + y₂ = (2)(2)
5 + y₂ = 4
y₂ = 4 - 5
= - 1
∴ if midpoint is (A,B) then midpoint is (13 , -1)