The sum of a number and twice its reciprocal is 3

The sum of a number and twice its reciprocal is 3

the phrase a number means an arbitrary variable, let's call it x.
x

The reciprocal of a number means we take 1 over that number:
1/x

Twice the reciprocal means we multiply 1/x by 2:
2/x

The sum of a number and twice its reciprocal
x + 2/x

The word is means equal to, so we set x + 2/x equal to 3
x + 2/x = 3