Hey. Let me help you on this one.
If we take a closer look at the problem, Steven wants to make two different clothing pieces - a hat and a scarf using the same type of yarn bundle (amount requires doesn't matter). Each piece requires a different amount of yarn. For example, a hat needs 3/4 of the bundle, while a scarf is supposed to be knitted with a half of the yarn.
Let's start off by converting everything to a fraction with the same denominator - number below numerator.
Hat -

Scarf - one half, or

As we can see, our denominators are different. Let's multiply

by 2 in order for us to raise the denominator to four, since two times two is four.
We must not forget to multiply the numerator by two as well - whatever is multiplied in a fraction, it's to be multiplied in both parts.

Awesome. Now, that we know both values needed for the clothing pieces, let's add them together.

When adding fractions, we don't touch denominators. Remember this golden rule!
Five fourths can also be transformed into one whole number, and one fourth.

.
That's it! We solved this problem. I am attaching a helpful picture for you to study this material.
Answer: 1 1/4 of yarn bundles are needed.