????????????????????

they are asking to plug the angle of that 'x' part of the triangle, into the Sin function to get some decimal approximation of Sin(x) Does it make better sense now, what they are asking?

you could you Law of sines or a side side side formula, to find the answer. Since i've been using Law of Sines all day on Brainly.... lot's of people don't know it :/ I'll use that.

recall law of Sines Sin(A) / a = Sin(B) / b where big "A" is the angle and little "a" is the length of the side opposite of that big "A" angle.

then

Sin(90) / 26 = Sin(x) / 10

notice that we'll get some very long decimal number equal to Sin(x).. which is what we want

I happen to know Sin(90) off the top of my head... and so should you.. it's 1

1/26 = Sin(x) / 10

10 / 26 = Sin(x)

0.3846153846 = Sin(x)

and I see our answer in the yellow square in your choice of answers... btw.. that's a very colorful math program :)