I believe that there will be two such points.
One point is 3/4ths of the way from (3,5) to (8,-3).
To find this point: the x-distance from 3 to 8 is 5; 3/4ths of 5 is 15/4, or 3.75, adding 3.75 onto 3 is 6.75
the y-distance from 5 to -3 is -8; 3/4ths of -8 is -6, adding -6 to 5 is -1
this point is (6.75, -1)
Checking: the distance from 3 to 6.75 is 3.75; the distance from 6.75 to 8 is 1.25; 3.75 = 3 x 1.25
the distance from 5 to -1 is -6; the distance from -1 to -3 is -2; -6 = 3 x -2
The other point is past (8,-3).
To find this point: the x-distance from 3 past 8 must have value 3, the x-distance from 8 away from 3 must have value 1. Dividing the distance from 3 to 8 into 2 parts, each part has value 2.5; add 2.5 onto 8 gives 10.5.
the y-distance from 5 to -3 has 2 parts, each part having value -4; add -4 onto -3 gives -7
this point is (10.5,-7)
Checking: the distance from 3 to 10.25 is 7.25; the distance from 8 to 10.25 is 2.25; 7.25 = 3 x 2.25
the distance from 5 to -7 is -12; the distance from -7 to -3 is -4; -12 = 3 x -4