n 10 years , a will be twice as old as b was 10 years ago . if a is now 9 years older than b the present age of b is
a + 10 = 2 ( b - 10 ) . . . . . . . . ( 1 ) a = b + 9 . . . . . . . . . ( 2 ) from equations . 1 & 2 we get b = 39 a will be 39 + 9 = 48 years old . answer : e
add(9, add(add(multiply(const_2, 10), 10), 9))