A quarter of a number is greater than or equal to 38

A quarter of a number is greater than or equal to 38.

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

A quarter of a number means 1/4, so we have:
x/4

The phrase is greater than or equal to means an inequality, so we use the >= sign in relation to 38:
x/4 >= 38 <-- This is our algebraic expression

If you want to solve this inequality, we type it in the search engine to get:
x >= 152