Concept:Use variables for present ages and form equations from the given age relations.
Explanation:Let Anil's present age be
x years and his father's present age be
y years.
Given: Anil is one-fourth his father's age.
So,
x=41​y.
After 18 years, Anil's age will be
x+18 and his father's age will be
y+18.
At that time, Anil will be half his father's age.
So,
x+18=21​(y+18).
Substitute
x=41​y into this equation:
41​y+18=21​(y+18)⇒4y​+18=2y​+9⇒2y​−4y​=18−9⇒4y​=9⇒y=36 years.
Answer:The present age of Anil's father is
36 years, which is option B.