Maximum and minimum of two concurrent forces occur when the forces are collinear. Maximum occurs when they are in the same direction, and minimum occurs when they are opposite in directions.
This reduces the problem to a sum an difference problem.
A+B=45
A-B=5
So
A=(45+5)/2=25
B=(45-5)/2=20
Check:
maximum=25+20=45
minimum=25-20=5
ok
