Given that abcd is a rhombus, what is the value of x?

a. 28
b. 56
c. 48.5
d. 18
e. 36
f. cannot be determined

  D.  18

Step-by-step explanation:

∠DAC ≅ ∠BCA and the diagonals cross at right angles, so the two marked angles are complementary.

  (5x -18) +x = 90

  6x = 108 . . . . . . . . . simplify, add 18

  x = 18 . . . . . . . . . . . divide by 6

i think it's ф or x=6,-6

step-by-step explanation:

-x^2=-36

x^2=-36

ф

or

if you mean by : -(x^2)=-36

it'll be: x^2=36

x=6,x=-6

hope it'll ! have a good day!

you for asking!