We're given the angle measure to be 46 for No. 8. The length of 1 leg is x and the hypotenuse is 28.
We can use cosine to solve this. Since cosine is adjacent over hypotenuse, we can do cos(46) = x/28. Cross multiply to get cos(46)*28 = x. That solves to be 19.5
Using this principle allows us to solve the other ones. I'll let you figure them out.
TLDR: We can use the definition of trig functions to plug in what we know and place variables where we don't have enough information to find the length of a side.