If one of the rectangular component of a 50n force is 25n,find the other?

If you draw the indicated vectors you have a right triangle with hypotenuse equal to 50 and one side equal to 25. The other side is found by the Pythagorean theorem:

x^2 + 25^2 = 50^2

x^2 = 2500 - 625 = 1875

x = sqr(1875) = 43.3

You need to be perfectly prepared in algebra to study physics.