Can someone help me with this geometry question I don’t understand it

When answering questions like these, it helps to draw arrows,, the variable will always be on top, so in this situation you would draw an arrow from the a to the 10 and an arrow from the 38 to the 12 making them both fractions, you would then cross multiply, after cross multiplying you would get 12a=380 then you would divide by 12 equaling 31.6

The correct answer is d, hope this