The black triangles are similar. Find the value of x. 28
х
12 d
21
The value of x is
(just type a number in the box)
please help!!

the complete question is
Julia owes her dad $12. She wants a new blouse that just went on sale, so she borrows $20 from her sister. She pays her father $5 and spends the rest on the blouse. Which statement is true?
A. Julia’s money status is $8 because she started at –$12 and borrowed $20.
B. Julia’s money status is –$7 because she started at –$12, got $20, but only paid $5 of her debt.
C. Julia’s money status is –$27 because she started at –$12, borrowed $20, but paid off $5.
D. Julia’s money status is –$32 because she began at –$12 and borrowed $20.

we know that
Julia owes her dad $12 already and again she borrowed $20 from her sister
So,
total debt = $12+$20=$ 32.
And,
she paid $5 only to her father.
So,
Her money status is
 -32+5 = -$27 

the answer is the option 
C. Julia’s money status is –$27 because she started at –$12, borrowed $20, but paid off $5.