Answer:
D: 15
Step-by-step explanation:
Ok, by looking at the first equation, you know that one triangle equals 10. By looking at the second one, you see that two circles equal 10, since 20- triangle(10) equals 10. This means a circle has to equal 5. looking at the third one, the answer is 13, and a circle is 5, so 13-5=8. Two squares equal 8. the last one shows one triangle, one circle, and a half square. From the third one, you know that one square equals 4, so a half square equals two. I do not know why this logic doesn't match with the answers, since 10(triangle) plus 5(circle) and 2(half square) is 17, but in terms of what makes sense and just matching it with the answers provided, I say go with the third option.
) by
and 
, which yields
