1.  Notice I changed your incorrect formulation.


2.  Let f = father's present age; s = son's present age.

    Then 4 years ago the father's age was f - 4; the son's age was s - 4, and

     = 7.    (1)

    In 16 years the father's age will be f + 16; the sons age will be s + 16, and

     = 2.   (2)

    You need to solve this system of two equations in two unknowns (1) and (2).

3.  Let us simplify it. Multiply (1) by (s-2) (both sides). Multiply (2) by (s+16) (both sides). You will get

    f -  4 = 7*(s-4),     (3)
    f + 16 = 2*(s+16).    (4)

    Next express f = 7*(s-4) + 4 from (3) and substitute it into (4). You will get

    7*(s-4) + 4 + 16 = 2*(s+16).

    Simplify it step by step:

    7s - 28 + 4 + 16 = 2s + 32,
    7s - 2s = 32 + 28 - 4 - 16,
    5s = 40,

    s =  = 8.

    Hence, son is 8 years now.
    Then father's age is f = 7*(s-4)+4 = 7*4+4 = 32.

Answer. Father's present age is 32 years. Son's present age is 8 years.