the greatest and the least resultant of 2 forces acting at a point is 10newton and 6newton respectively.
if each force is increased by 3newton, find the resultant of new forces when acting at a point at an angle of 90degree with each other.

Let, 1st force = a

2nd force = b

A.T.Q,

a+b = 10

a-b = 6

Calculate for a & b, you'll get a=8 & b= 2

After increasing by 3, it'll be a = 8+3 = 11 & b=2+3 = 5

Resultant force at 90 degree angle = 11+5 = 16 Newtons

The solution would be like this for this specific problem:

if resultant of new forces when acting at a point at an angle of 90Degrees with each other:
(x^2+y^2+2xycos90*)^1/2
=(121+25)^1/2
=146^1/2
=12.08N

I am hoping that this answer has satisfied your query and it will be able to help you in your endeavor, and if you would like, feel free to ask another question.