Step-by-step explanation: Ok lets go step by step then.
Hery is 4 years younger tha linda, that means that if H is henry's ange and L linda's age.
L - H = 4.
and Linda has 20 years, so:
20 - H = 4
if we subtract 20 of each side of the equation we get:
-H = 4 - 20 = -16
If we multiply by -1, so we have positive numbers in both sides.
H = 16.
so Henry is 16 years old.