Original: I hope to study mathematics, because I like the fact that mathematics can help in virtually every professional field.
At a minimum, you need to remove your comma splice and drop "like":
Better: I hope to study mathematics because it can help in virtually every professional field.
In America (USA), it's stronger to state what you "want" than "hope". Be specific. IMO, "virtually every" has become cliche and gets confused with the now stronger meaning of "virtual" as in "virtual reality". Also, the phrase "it can help" is too anthropomorphic and sounds naive:
Best: I want to study mathematics because of its broad application across many fields that I'm interested in including computing, economics, human behavior, and game theory.
FYI - Many people want to study mathematics because of a love and passion for mathematics itself as an art, a science, and a way to explore the boundaries of self and transcendent knowledge. Just thought you might like to know that math has "more" use than just being helpful in professional fields. It's good enough to study on its own without using it anywhere!