That's an expression, so the only thing you can do is simplify it, but that already looks simplified.
46%d+57%y=55%x42
x+y=42
Find y
x=42-y
46%(42-y)+57%y=23.1
19.31-46%y+57%y=23.1
11%y=23.1-19.31
11%y=3.79
y=34
The answer is D
The blanks are weird. I don't understand them!
I am attaching an image with the two solutions represented by the blue areas highlighted in your original graphs. Let me know if you have questions.